13.8 Automatic Power Control
The ONS 15454 automatic power control (APC) feature performs the following functions:
- Maintains constant per channel power when desired or accidental changes to the number of channels occur. Constant per channel power increases optical network resilience.
- Compensates for optical network degradation (aging effects).
- Simplifies the installation and upgrade of DWDM optical networks by automatically calculating the amplifier setpoints.
Note APC algorithms manage the optical parameters of the OPT-BST, OPT-PRE, OPT-AMP-17-C, 32DMX, 40-DMX-C, 40-DMX-CE, 40-SMR1-C, 40-SMR2-C, OPT-BST-L, OPT-AMP-L, OPT-AMP-C, and 32DMX-L cards.
Amplifier software uses a control gain loop with fast transient suppression to keep the channel power constant regardless of any changes in the number of channels. Amplifiers monitor the changes to the input power and change the output power proportionately according to the calculated gain setpoint. The shelf controller software emulates the control output power loop to adjust for fiber degradation. To perform this function, the TCC2/TCC2P/TCC3/TNC/TNCE/TSC/TSCE needs to know the channel distribution, which is provided by a signaling protocol, and the expected per channel power, which you can provision. The TCC2/TCC2P/TCC3/TNC/TNCE/TSC/TSCE card compares the actual amplifier output power with the expected amplifier output power and modifies the setpoints if any discrepancies occur.
13.8.1 APC at the Amplifier Card Level
In constant gain mode, the amplifier power out control loop performs the following input and output power calculations, where G represents the gain and t represents time.
Pout (t) = G * Pin (t) (mW)
Pout (t) = G + Pin (t) (dB)
In a power-equalized optical system, the total input power is proportional to the number of channels. The amplifier software compensates for any variation of the input power due to changes in the number of channels carried by the incoming signal.
Amplifier software identifies changes in the read input power in two different instances, t1 and t2, as a change in the traffic being carried. The letters m and n in the following formula represent two different channel numbers. Pin/ch represents the input power per channel.
Pin (t1)= nPin/ch
Pin (t2) = mPin/ch
Amplifier software applies the variation in the input power to the output power with a reaction time that is a fraction of a millisecond. This keeps the power constant on each channel at the output amplifier, even during a channel upgrade or a fiber cut.
The per channel power and working mode (gain or power) are set by automatic node setup (ANS). The provisioning is conducted on a per-side basis. A preamplifier or a booster amplifier facing Side i is provisioned using the Side i parameters present in the node database, where i - A, B, C, D, E, F, G, or H.
Starting from the expected per channel power, the amplifiers automatically calculate the gain setpoint after the first channel is provisioned. An amplifier gain setpoint is calculated in order to make it equal to the loss of the span preceding the amplifier itself. After the gain is calculated, the setpoint is no longer changed by the amplifier. Amplifier gain is recalculated every time the number of provisioned channels returns to zero. If you need to force a recalculation of the gain, move the number of channels back to zero.
13.8.2 APC at the Shelf Controller Layer
Amplifiers are managed through software to control changes in the input power caused by changes in the number of channels. The software adjusts the output total power to maintain a constant per channel power value when the number of input channel changes.
Changes in the network characteristics have an impact on the amplifier input power. Changes in the input power are compensated for only by modifying the original calculated gain, because input power changes imply changes in the span loss. As a consequence, the gain to span loss established at amplifier start-up is no longer satisfied, as shown in Figure 13-23.
Figure 13-23 Using Amplifier Gain Adjustment to Compensate for System Degradation
In Figure 13-23, Node 1 and Node 2 are equipped with booster amplifiers and preamplifiers. The input power received at the preamplifier on Node 2 (Pin2) depends on the total power launched by the booster amplifier on Node1, Pout1(n) (where n is the number of channels), and the effect of the span attenuation (L) between the two nodes. Span loss changes due to aging fiber and components or changes in operating conditions. The power into Node 2 is given by the following formula:
Pin2 = LPout1(n)
The phase gain of the preamplifier on Node 2 (GPre-2) is set during provisioning in order to compensate for the span loss so that the Node 2 preamplifier output power (Pout-Pre-2) is equal to the original transmitted power, as represented in the following formula:
Pout-Pre-2 = L x GPre-2 x Pout1(n)
In cases of system degradation, the power received at Node 2 decreases due to the change of span insertion loss (from L to L'). As a consequence of the preamplifier gain control working mode, the Node 2 preamplifier output power (Pout-Pre-2) also decreases. The goal of APC at the shelf controller layer is simply to detect if an amplifier output change is needed because of changes in the number of channels or to other factors. If factors other than changes in the number of channels occur, APC provisions a new gain at the Node 2 preamplifier (GPre-2') to compensate for the new span loss, as shown in the formula:
GPre-2' = GPre-2 (L/ L') = GPre-2 + [Pout-Pre-2 –Exp(Pout-Pre-2)]
Generalizing on the above relationship, APC is able to compensate for system degradation by adjusting working amplifier gain or variable optical attenuation (VOA) and to eliminate the difference between the power value read by the photodiodes and the expected power value. The expected power values are calculated using:
- Provisioned per channel power value
- Channel distribution (the number of express, add, and drop channels in the node)
- ASE estimation
Channel distribution is determined by the sum of the provisioned and failed channels. Information about provisioned wavelengths is sent to APC on the applicable nodes during circuit creation. Information about failed channels is collected through a signaling protocol that monitors alarms on ports in the applicable nodes and distributes that information to all the other nodes in the network.
ASE calculations purify the noise from the power level reported from the photodiode. Each amplifier can compensate for its own noise, but cascaded amplifiers cannot compensate for ASE generated by preceding nodes. The ASE effect increases when the number of channels decreases; therefore, a correction factor must be calculated in each amplifier of the ring to compensate for ASE build-up.
APC is a network-level feature that is distributed among different nodes. An APC domain is a set of nodes that is controlled by the same instance of APC at the network level. An APC domain optically identifies a portion of the network that can be independently regulated. An optical network can be divided into several different domains, with the following characteristics:
- Every domain is terminated by two node sides. The node sides terminating domains are:
– Terminal node (any type)
– ROADM node
– Hub node
– Cross-connect (XC) termination mesh node
– Line termination mesh node
- APC domains are shown in both Cisco Transport Controller (CTC) and Transaction Language One (TL1).
- In CTC, domains are shown in the network view and reported as a list of spans. Each span is identified by a node/side pair, for example:
APC Domain Node_1 Side A, Node_4 Side B
+ Span 1: Node_1 Side A, Node_2 Side B
+ Span 2: Node_2 Side A, Node_3 Side B
+ Span 3: Node_3 Side A, Node_4 Side B
- APC domains are not refreshed automatically; instead, they are refreshed using a Refresh button.
Inside a domain, the APC algorithm designates a master node that is responsible for starting APC hourly or every time a new circuit is provisioned or removed. Every time the master node signals APC to start, gain and VOA setpoints are evaluated on all nodes in the network. If corrections are needed in different nodes, they are always performed sequentially following the optical paths starting from the master node.
APC corrects the power level only if the variation exceeds the hysteresis thresholds of +/– 0.5 dB. Any power level fluctuation within the threshold range is skipped since it is considered negligible. Because APC is designed to follow slow time events, it skips corrections greater than 3 dB. This is the typical total aging margin that is provisioned during the network design phase. After you provision the first channel or the amplifiers are turned up for the first time, APC does not apply the 3 dB rule. In this case, APC corrects all the power differences to turn up the node.
To avoid large power fluctuations, APC adjusts power levels incrementally. The maximum power correction is +/– 0.5 dB. This is applied to each iteration until the optimal power level is reached. For example, a gain deviation of 2 dB is corrected in four steps. Each of the four steps requires a complete APC check on every node in the network. APC can correct up to a maximum of 3 dB on an hourly basis. If degradation occurs over a longer time period, APC compensates for it by using all margins that you provision during installation.
If no margin is available, adjustments cannot be made because setpoints exceed the ranges. APC communicates the event to CTC, Cisco Transport Manager (CTM), and TL1 through an APC Fail condition. APC clears the APC fail condition when the setpoints return to the allowed ranges.
APC can be manually disabled. In addition, APC automatically disables itself when:
- An Hardware Fail (HF) alarm is raised by any card in any of the domain nodes.
- A Mismatch Equipment Alarm (MEA) is raised by any card in any of the domain nodes.
- An Improper Removal (IMPROPRMVL) alarm is raised by any card in any of the domain nodes.
- Gain Degrade (GAIN-HDEG), Power Degrade (OPWR-HDEG), and Power Fail (PWR-FAIL) alarms are raised by the output port of any amplifier card in any of the domain nodes.
- A VOA degrade or fail alarm is raised by any of the cards in any of the domain nodes.
- The signaling protocol detects that one of the APC instances in any of the domain nodes is no longer reachable.
The APC state (Enable/Disable) is located on every node and can be retrieved by the CTC or TL1 interface. If an event that disables APC occurs in one of the network nodes, APC is disabled on all the other nodes and the APC state changes to DISABLE - INTERNAL. The disabled state is raised only by the node where the problem occurred to simplify troubleshooting.
APC raises the following minor, non-service-affecting alarms at the port level in CTC, TL1, and Simple Network Management Protocol (SNMP):
- APC Out of Range—APC cannot assign a new setpoint for a parameter that is allocated to a port because the new setpoint exceeds the parameter range.
- APC Correction Skipped—APC skipped a correction to one parameter allocated to a port because the difference between the expected and current values exceeds the +/– 3 dB security range.
- APC Disabled—APC is disabled, either by a user or internal action.
After the error condition is cleared, the signaling protocol enables APC on the network and the APC DISABLE - INTERNAL condition is cleared. Because APC is required after channel provisioning to compensate for ASE effects, all optical channel network connection (OCHNC) and optical channel client connection (OCHCC) circuits that you provision during the disabled APC state are kept in the Out-of-Service and Autonomous, Automatic In-Service (OOS-AU,AINS) (ANSI) or Unlocked-disabled,automaticInService (ETSI) service state until APC is enabled. OCHNCs and OCHCCs automatically go into the In-Service and Normal (IS-NR) (ANSI) or Unlocked-enabled (ETSI) service state only after APC is enabled.
13.8.3 APC in a Raman Node with Post-Amplifiers
After the Raman gain is calculated and the Raman and OSC links are turned up, APC performs the following sequence of events:
1. The line amplifier that is downstream of the OPT-RAMP-C or OPT-RAMP-CE card is the first card that the APC regulates. The line amplifier is configured as OPT-PRE in ROADM nodes or as OPT-LINE in OLA nodes.
After Automatic Power Reduction (APR) is implemented, the working mode of the line amplifier is forced to Control Power and remains in the same mode until all the node regulations are complete. This ensures that the calculation of the Gain setpoint is accurate during Raman node internal regulations. The amplifier signal output power is regulated using the Power (LINE-TX port) setpoint.
2. The APC changes the Gain setpoint of the embedded EDFA to reach the value that is equal to Power (DC-TX port) value multiplied by the number of active channels.
The APC can set the Gain setpoint of the embedded EDFA (G EDFA) in the following ranges:
– OPT-RAMP-C 10 dB < G EDFA < 18 dB
– OPT-RAMP-CE 7 dB < G EDFA < 13 dB
The internal VOA is set to 0 dB on the DC-TX port. The VOA attenuation is set to zero because the actual DCU insertion loss is unknown until the optical payload is transmitted to the card. Therefore a proper attenuation setpoint cannot be estimated. When the attenuation value is set to 0 dB, it ensures that the system turns up in any circumstance.
3. After the G EDFA is set, APC regulates the power on the VOA (DC-TX port) of the OPT-RAMP-C or OPT-RAMP-CE card to match the target Power (COM-TX port) value, and accounts for the actual DCU loss.
4. After Steps 2 and 3 are completed, the optical power received on the line amplifier that is downstream of the OPT-RAMP-C or OPT-RAMP-CE card becomes fully regulated and stable. The Raman tilt and G EDFA tilt are fixed. The APC regulates the value of the Total Power on the LINE-TX port of the line amplifier and accounts for the ASE noise contribution.
5. After the value of the total power on the line amplifier becomes a stable value, APC stops the regulations and the automatic gain calculation procedure is completed on the line amplifier card. The TCC checks if the gain setpoint is within range and eventually changes the working mode of the OPT-RAMP-C or OPT-RAMP-CE card to Gain Control mode.
Note If the value of the Raman Total Power was manually provisioned or set by ANS instead of the Raman installation wizard, a fiber cut recovery procedure is automatically performed, before APC regulation.
13.8.4 APC in a Raman Node without Post-Amplifiers
After the Raman gain is calculated and the Raman and OSC links are turned up, APC performs the following sequence of events:
1. The APC adjusts the VOA attenuation of the OPT-RAMP-C or OPT-RAMP-CE card if the Total Power (LINE-TX port) does not match the expected value that is equal to the maximum power multiplied by the number of active channels. The VOA attenuation value on the OPT-RAMP-C or OPT-RAMP-CE cards is set to 15 dB. This value ensures that the system turns up in any circumstance.
2. If a short span is used, the embedded EDFA in the downstream node receives excessive input power and is unable to maintain proper per channel power value on its output port as the number of channels increase. The APC detects output power saturation on the EDFA of the downstream node and increases the value of the VOA attenuation on the upstream node thereby reducing the Power (LINE-TX port) value.
13.8.5 Managing APC
The APC status is indicated by four APC states shown in the node view status area:
- Enabled—APC is enabled.
- Disabled—APC was disabled manually by a user.
- Disable - Internal—APC has been automatically disabled for an internal cause.
- Not Applicable—The node is provisioned to Not DWDM, which does not support APC.
You can view the APC information and disable and enable APC manually on the Maintenance > DWDM > APC tab.
Caution When APC is disabled, aging compensation is not applied and circuits cannot be activated. Do not disable APC unless it is required for specific maintenance or troubleshooting tasks. Always enable APC as soon as the tasks are completed.
The APC subtab provides the following information:
- Position—The slot number, card, and port for which APC information is shown.
- Last Modification—Date and time APC parameter setpoints were last modified.
- Parameter—The parameter that APC last modified.
- Last Check—Date and time APC parameter setpoints were last verified.
- Side—The side where the APC information for the card and port is shown.
- State—The APC state.
A wrong use of maintenance procedures (for example, the procedures to be applied in case of fiber cut repair) can lead the system to raise the APC Correction Skipped alarm. The APC Correction Skipped alarm strongly limits network management (for example, a new circuit cannot be turned into IS). The Force APC Correction button helps to restore normal conditions by clearing the APC Correction Skipped alarm.
The Force APC Correction button must be used under the Cisco TAC surveillance since its misuse can lead to traffic loss.
The Force APC Correction button is available in the Card View > Maintenance > APC tab pane in CTC for the following cards:
- OPT-PRE
- OPT-BST-E
- OPT-BST
- OPT-AMP-C
- OPT-AMP-17C
- AD-xB
- AD-xC
- 40-SMR1-C
- 40-SMR2-C
This feature is not available for the TL1 interface.
13.11 Network Optical Safety
If a fiber break occurs on the network, automatic laser shutdown (ALS) automatically shuts down the OSCM and OSC-CSM OSC laser output power and the optical amplifiers contained in the OPT-BST, OPT-BST-E, OPT-BST-L, OPT-AMP-L, OPT-AMP-C, OPT-AMP-17-C, OPT-RAMP-C, OPT-RAMP-CE, 40-SMR1-C, and 40-SMR2-C cards, and the TX VOA in the protect path of the PSM card (in line protection configuration only). (Instead, the PSM active path will use optical safety mechanism implemented by the booster amplifier or OSC-CSM card that are mandatory in the line protection configuration.)
The Maintenance > ALS tab in CTC card view provide the following ALS management options for OSCM, OSC-CSM, OPT-BST, OPT-BST-E, OPT-BST-L, OPT-AMP-L, OPT-AMP-C, OPT-AMP-17-C, OPT-RAMP-C, OPT-RAMP-CE, 40-SMR1-C, 40-SMR2-C, and PSM (on the protect path, only in line protection configuration) cards:
- Disable—ALS is off. The OSC laser transmitter and optical amplifiers are not automatically shut down when a traffic outage loss of signal (LOS) occurs.
- Auto Restart—ALS is on. The OSC laser transmitter and optical amplifiers automatically shut down when traffic outages (LOS) occur. It automatically restarts when the conditions that caused the outage are resolved. Auto Restart is the default ALS provisioning for OSCM, OSC-CSM, OPT-BST, OPT-BST-E, OPT-BST-L, OPT-AMP-L, OPT-AMP-C, OPT-AMP-17-C, OPT-RAMP-C, OPT-RAMP-CE, 40-SMR1-C, 40-SMR2-C, and PSM (on the protect path, only in line protection configuration) cards.
- Manual Restart—ALS is on. The OSC laser transmitter and optical amplifiers automatically shut down when traffic outages (LOS) occur. However, the laser must be manually restarted when conditions that caused the outage are resolved.
- Manual Restart for Test—Manually restarts the OSC laser transmitter and optical amplifiers for testing.
13.11.1 Automatic Laser Shutdown
When ALS is enabled on OPT-BST, OPT-BST-E, OPT-BST-L, OPT-AMP-L, OPT-AMP-C, OPT-AMP-17-C, OPT-RAMP-C, OPT-RAMP-CE, 40-SMR1-C, 40-SMR2-C, PSM (on the protect path, only in line protection configuration), OSCM, OSC-CSM, TNC, and TNCE cards, a network safety mechanism will occur in the event of a system failure. ALS provisioning is also provided on the transponder (TXP) and muxponder (MXP) cards. However, if a network uses ALS-enabled OPT-BST, OPT-BST-E, OPT-BST-L, OPT-AMP-L, OPT-AMP-C, OPT-AMP-17-C, OPT-RAMP-C, OPT-RAMP-CE, 40-SMR1-C, 40-SMR2-C, PSM (on the protect path, only in line protection configuration), OSCM, and OSC-CSM cards, ALS does not need to be enabled on the TXP cards or MXP cards. ALS is disabled on TXP and MXP cards by default and the network optical safety is not impacted.
If TXP and MXP cards are connected directly to each other without passing through a DWDM layer, ALS should be enabled on them. The ALS protocol goes into effect when a fiber is cut, enabling some degree of network point-to-point bidirectional traffic management between the cards.
If ALS is disabled on the OPT-BST, OPT-BST-E, OPT-BST-L, OPT-AMP-L, OPT-AMP-C, OPT-AMP-17-C, OPT-RAMP-C, OPT-RAMP-CE, 40-SMR1-C, 40-SMR2-C, PSM (on the protect path, only in line protection configuration), OSCM, and OSC-CSM cards (the DWDM network), ALS can be enabled on the TXP and MXP cards to provide laser management in the event of a fiber break in the network between the cards.
13.11.2 Automatic Power Reduction
Automatic power reduction (APR) is controlled by the software and is not user configurable. During amplifier restart after a system failure, the amplifier (OPT-BST, for example) operates in pulse mode and an APR level is activated so that the Hazard Level 1 power limit is not exceeded. This is done to ensure personnel safety.
When a system failure occurs (cut fiber or equipment failure, for example) and ALS Auto Restart is enabled, a sequence of events is placed in motion to shut down the amplifier laser power, then automatically restart the amplifier after the system problem is corrected. As soon as a loss of optical payload and OSC is detected at the far end, the far-end amplifier shuts down. The near-end amplifier then shuts down because it detects a loss of payload and the OSC shuts down due to the far-end amplifier shutdown. At this point, the near end attempts to establish communication to the far end using the OSC laser transmitter. To do this, the OSC emits a two-second pulse at very low power (maximum of 0 dBm) and waits for a similar two-second pulse in response from the far-end OSC laser transmitter. If no response is received within 100 seconds, the near end tries again. This process continues until the near end receives a two-second response pulse from the far end, indicating the system failure is corrected and full continuity in the fiber between the two ends exists.
After the OSC communication is established, the near-end amplifier is configured by the software to operate in pulse mode at a reduced power level. It emits a nine-second laser pulse with an automatic power reduction to +8 dBm. (For 40-SMR1-C and 40-SMR2-C cards, the pulse is not +8 dBm but it is the per channel power setpoint.) This level assures that Hazard Level 1 is not exceeded, for personnel safety, even though the establishment of successful OSC communication is assurance that any broken fiber is fixed. If the far-end amplifier responds with a nine-second pulse within 100 seconds, both amplifiers are changed from pulse mode at reduced power to normal operating power mode.
For a direct connection between TXP or MXP cards, when ALS Auto Restart is enabled and the connections do not pass through a DWDM layer, a similar process takes place. However, because the connections do not go through any amplifier or OSC cards, the TXP or MXP cards attempt to establish communication directly between themselves after a system failure. This is done using a two-second restart pulse, in a manner similar to that previously described between OSCs at the DWDM layer. The power emitted during the pulse is below Hazard Level 1.
APR is also implemented on the PSM card (on the protect path, only in line protection configuration). In the PSM line protection configuration, when a system failure occurs on the working path (cut fiber or equipment failure, for example), the ALS and APR mechanisms are implemented by the booster amplifier or the OSC-CSM card. Alternately, when a system failure occurs on the protect path, and ALS Auto Restart is enabled on the PSM card, a sequence of events is placed in motion to shut down the TX VOA on the protect path, and then automatically restart it after the system failure is corrected. During protect path restart, the TX VOA on the protect path operates in pulse mode and limits the power to maximum +8 dBm so that the Hazard Level 1 power limit is not exceeded on protect TX path.
When ALS is disabled, the warning Statement 1056 is applicable.
Warning Invisible laser radiation may be emitted from the end of the unterminated fiber cable or connector. Do not view directly with optical instruments. Viewing the laser output with certain optical instruments (for example, eye loupes, magnifiers, and microscopes) within a distance of 100 mm may pose an eye hazard. Statement 1056
Note If you must disable ALS, verify that all fibers are installed in a restricted location. Enable ALS immediately after finishing the maintenance or installation process.
Note For the line amplifier to start up automatically, disable the ALS on the terminal node that is unidirectional.
13.11.3 Network Optical Safety on OPT-RAMP-C and OPT-RAMP-CE Cards
Optical safety on the OPT-RAMP-C and OPT-RAMP-CE cards is implemented in the RAMAN-TX and COM-TX ports. RAMAN-TX will report safety settings associated to the Raman pump while the COM-TX port will report safety settings associated with the embedded EDFA.
13.11.3.1 RAMAN-TX Settings on Raman Pump
The Raman pump is automatically turned off as soon as the LOS alarm is detected on the LINE-RX port. The Raman pump is automatically turned on at APR power every 100 secs for a duration of 9 seconds at a pulse power of at 8 dBm, as soon as the LINE-RX port is set to IS-NR/unlocked-enabled.
Note Optical safety cannot be disabled on the OPT-RAMP-C and OPT-RAMP-CE cards and cannot be disabled on OSCM cards when connected to a OPT-RAMP-C or OPT-RAMP-CE card.
The system periodically verifies if the signal power is present on the LINE-RX port. If signal power is present, the following occurs:
- Pulse duration is extended.
- Raman pumps are turned on at APR power, if the laser was shut down.
The Raman power is then moved to setpoint if power is detected for more than 10 seconds. During Automatic Laser Restart (ALR) the safety is enabled. The laser is automatically shut down if LOS is detected on the receiving fiber. In general Raman pump turns on only when Raman signals are detected. However, the Raman pump can be configured to turn on to full power even when OSC power is detected for more than 9 seconds on OSC-RX port.
13.11.3.2 COM-TX Safety Setting on EDFA
EDFA is shutdown automatically under the following conditions:
- The Raman pumps shut down.
- An LOS-P alarm is detected on the COM-RX port.
If EDFA was shut down because of Raman pump shut down, the EDFA restarts by automatically turning on the EDFA lasers as soon as the Raman loop is closed.
- Pulse duration: 9 seconds
- Pulse power: 8 dB (maximum APR power foreseen by safety regulation)
- Exit condition: Received power detected on the DC-RX port at the end of APR pulse. If power is detected on DC-RX (so DCU is connected) EDFA moves to set-point; otherwise, it keeps 9 dB as the output power at restart
- EDFA moves to the power setpoint when power is detected on the DC-RX port.
If EDFA was shutdown because of an LOS-P alarm. The EDFA restarts by automatically turning on the EDFA laser as soon as an LOS-P alarm on the COM-RX port is cleared, and the Raman loop is closed.
- Pulse duration: 9 seconds
- Pulse power: 8 dB (maximum APR power foreseen by safety regulation)
- Exit condition: Received power detected on the LINE-RX port at the end of the APR pulse
Warning All ONS 15454 users must be properly trained on laser safety hazards in accordance with IEC 60825-2, or ANSI Z136.1.
13.11.4 Fiber Cut Scenarios
In the following paragraphs, four ALS scenarios are given:
13.11.4.1 Scenario 1: Fiber Cut in Nodes Using OPT-BST/OPT-BST-E Cards
Figure 13-26 shows nodes using OPT-BST/OPT-BST-E cards with a fiber cut between them.
Figure 13-26 Nodes Using OPT-BST/OPT-BST-E Cards
Two photodiodes at Node B monitor the received signal strength for the optical payload and OSC signals. When the fiber is cut, an LOS is detected at both of the photodiodes. The AND function then indicates an overall LOS condition, which causes the OPT-BST/OPT-BST-E transmitter, OPT-PRE transmitter, and OSCM lasers to shut down. This in turn leads to an LOS for both the optical payload and OSC at Node A, which causes Node A to turn off the OSCM, OPT-PRE transmitter, and OPT-BST/OPT-BST-E transmitter lasers. The sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 13-26):
1. Fiber is cut.
2. The Node B power monitoring photodiode detects a Loss of Incoming Payload (LOS-P) on the OPT-BST/OPT-BST-E card. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
3. On the OPT-BST/OPT-BST-E card, the simultaneous LOS-O and LOS-P detection triggers a command to shut down the amplifier. CTC reports an LOS alarm (loss of continuity), while LOS-O and LOS-P are demoted. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
4. The OPT-BST/OPT-BST-E card amplifier is shut down within one second.
5. The OSCM laser is shut down.
6. The OPT-PRE card automatically shuts down due to a loss of incoming optical power.
7. The Node A power monitoring photodiode detects a LOS-O on the OPT-BST/OPT-BST-E card and the OSCM card detects a LOS (OC3) at the SONET layer. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
8. The Node A power monitoring photodiode detects a LOS-P on the OPT-BST/OPT-BST-E card. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
9. On the OPT-BST/OPT-BST-E, the simultaneous LOS-O and LOS-P detection triggers a command to shut down the amplifier. CTC reports an LOS alarm (loss of continuity), while LOS-O and LOS-P are demoted. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
10. The OPT-BST/OPT-BST-E card amplifier is shut down within one second.
11. The OSCM laser is shut down.
12. The Node A OPT-PRE card automatically shuts down due to a loss of incoming optical power.
When the fiber is repaired, either an automatic or manual restart at the Node A OPT-BST/OPT-BST-E transmitter or at the Node B OPT-BST/OPT-BST-E transmitter is required. A system that has been shut down is reactivated through the use of a restart pulse. The pulse is used to signal that the optical path has been restored and transmission can begin. For example, when the far end, Node B, receives a pulse, it signals to the Node B OPT-BST/OPT-BST-E transmitter to begin transmitting an optical signal. The OPT-BST/OPT-BST-E receiver at Node A receives that signal and signals the Node A OPT-BST/OPT-BST-E transmitter to resume transmitting.
Note During a laser restart pulse, APR ensures that the laser power does not exceed Class 1 limits. See the “Automatic Power Reduction” section for more information about APR.
13.11.4.2 Scenario 2: Fiber Cut in Nodes Using OSC-CSM Cards
Figure 13-27 shows nodes using OSC-CSM cards with a fiber cut between them.
Figure 13-27 Nodes Using OSC-CSM Cards
Two photodiodes at the Node B OSC-CSM card monitor the received signal strength for the received optical payload and OSC signals. When the fiber is cut, LOS is detected at both of the photodiodes. The AND function then indicates an overall LOS condition, which causes the Node B OSC laser to shut down and the optical switch to block traffic. This in turn leads to LOS for both the optical payload and OSC signals at Node A, which causes Node A to turn off the OSC laser and the optical switch to block outgoing traffic. The sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 13-27):
1. Fiber is cut.
2. The Node B power monitoring photodiode detects a LOS-P on the OSC-CSM card. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
3. On the OSC-CSM, the simultaneous LOS-O and LOS-P detection triggers a change in the position of the optical switch. CTC reports a LOS alarm (loss of continuity), while LOS-O and LOS-P are demoted. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
4. The optical switch blocks outgoing traffic.
5. The OSC laser is shut down.
6. The Node A power monitoring photodiode detects a LOS-O on the OSC-CSM card. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
7. The Node A power monitoring photodiode detects a LOS-P on the OSC-CSM card. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
8. On the OSC-CSM, the simultaneous LOS-O and LOS-P detection triggers a change in the position of the optical switch. CTC reports a LOS alarm (loss of continuity), while LOS-O and LOS-P are demoted. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
9. The OSC laser is shut down.
10. The optical switch blocks outgoing traffic.
When the fiber is repaired, either an automatic or manual restart at the Node A OSC-CSM card OSC or at the Node B OSC-CSM card OSC is required. A system that has been shut down is reactivated through the use of a restart pulse. The pulse indicates the optical path is restored and transmission can begin. For example, when the far-end Node B receives a pulse, it signals to the Node B OSC to begin transmitting its optical signal and for the optical switch to pass incoming traffic. The OSC-CSM at Node A then receives the signal and tells the Node A OSC to resume transmitting and for the optical switch to pass incoming traffic.
13.11.4.3 Scenario 3: Fiber Cut in Nodes Using OPT-BST-L Cards
Figure 13-28 shows nodes using OPT-BST-L cards with a fiber cut between them.
Figure 13-28 Nodes Using OPT-BST-L Cards
Two photodiodes at Node B monitor the received signal strength for the optical payload and OSC signals. When the fiber is cut, an LOS is detected at both of the photodiodes. The AND function then indicates an overall LOS condition, which causes the OPT-BST-L transmitter and OSCM lasers to shut down. This in turn leads to an LOS for both the optical payload and the OSC at Node A, which causes Node A to turn off the OSCM OSC transmitter and OPT-BST-L amplifier lasers. The sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 13-28):
1. Fiber is cut.
2. The Node B power monitoring photodiode detects an LOS-P on the OPT-BST-L card. For more information on alarms, refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
3. On the OPT-BST-L card, the simultaneous LOS-O and LOS-P detection triggers a command to shut down the amplifier. CTC reports an LOS alarm (loss of continuity), while LOS-O and LOS-P are demoted. For more information on alarms, refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
4. The OPT-BST-L card amplifier is shut down within one second.
5. The OSCM laser is shut down.
6. The OPT-AMP-L, OPT-AMP-C, or OPT-AMP-17-C card automatically shuts down due to a loss of incoming optical power.
7. The Node A power monitoring photodiode detects an LOS-O on the OPT-BST-L card and the OSCM card detects an LOS (OC3) at the SONET layer. For more information on alarms, refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
8. The Node A power monitoring photodiode detects an LOS-P on the OPT-BST-L card. For more information on alarms, refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
9. On the OPT-BST-L, the simultaneous LOS-O and LOS-P detection triggers a command to shut down the amplifier. CTC reports an LOS alarm (loss of continuity), while the LOS-O and LOS-P are demoted. For more information on alarms, refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
10. The OPT-BST-L card amplifier is shut down within one second.
11. The OSCM laser is shut down.
12. The Node A OPT-AMP-L, OPT-AMP-C, or OPT-AMP-17-C card automatically shuts down due to an LOS for the incoming optical power.
When the fiber is repaired, either an automatic or manual restart at the Node A OPT-BST-L transmitter or at the Node B OPT-BST-L transmitter is required. A system that has been shut down is reactivated through the use of a restart pulse. The pulse indicates the optical path is restored and transmission can begin. For example, when the far end, Node B, receives a pulse, it signals to the Node B OPT-BST-L transmitter to begin transmitting an optical signal. The OPT-BST-L receiver at Node A receives that signal and signals the Node A OPT-BST-L transmitter to resume transmitting.
Note During a laser restart pulse, APR ensures that the laser power does not exceed Class 1 limits. See the “Automatic Power Reduction” section for more information about APR.
13.11.4.4 Scenario 4: Fiber Cut in Nodes Using OPT-AMP-L, OPT-AMP-C, OPT-AMP-17-C (OPT-LINE Mode), 40-SMR1-C, or 40-SMR2-C Cards
Figure 13-29 shows nodes using OPT-AMP-L, OPT-AMP-C, OPT-AMP-17-C (in OPT-LINE mode), 40-SMR1-C, or 40-SMR2-C cards with a fiber cut between them.
Note A generic reference to the OPT-AMP card refers to the OPT-AMP-L, OPT-AMP-17-C, OPT-AMP-C, 40-SMR1-C, or 40-SMR2-C cards.
Figure 13-29 Nodes Using OPT-AMP Cards
Two photodiodes at Node B monitor the received signal strength for the optical payload and OSC signals. When the fiber is cut, an LOS is detected at both of the photodiodes. The AND function then indicates an overall LOS condition, which causes the OPT-AMP card amplifier transmitter and OSCM card OSC lasers to shut down. This in turn leads to an LOS for both the optical payload and OSC at Node A, which causes Node A to turn off the OSCM card OSC and OPT-AMP card amplifier lasers. The sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 13-29):
1. Fiber is cut.
2. The Node B power monitoring photodiode detects an LOS-P on the OPT-AMP card. For more information on alarms, refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
3. On the OPT-AMP card, the simultaneous LOS-O and LOS-P detection triggers a command to shut down the amplifier. CTC reports an LOS alarm (loss of continuity), while LOS-O and LOS-P are demoted. For more information on alarms, refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
4. The OPT-AMP card amplifier is shut down within one second.
5. The OSCM card laser is shut down.
6. The Node A power monitoring photodiode detects an LOS-O on the OPT-AMP card and the OSCM card detects an LOS (OC3) at the SONET layer. For more information on alarms, refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
7. The Node A power monitoring photodiode detects an LOS-P on the OPT-AMP card. For more information on alarms, refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
8. On the OPT-AMP card, the simultaneous LOS-O and LOS-P detection triggers a command to shut down the amplifier. CTC reports an LOS alarm (loss of continuity), while LOS-O and LOS-P are demoted. For more information on alarms, refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
9. The OPT-AMP card amplifier is shut down within one second.
10. The OSCM card laser is shut down.
When the fiber is repaired, either an automatic or manual restart at the Node A OPT-AMP card transmitter or at the Node B OPT-AMP card transmitter is required. A system that has been shut down is reactivated through the use of a restart pulse. The pulse indicates that the optical path is restored and transmission can begin. For example, when the far end, Node B, receives a pulse, it signals to the Node B OPT-AMP card transmitter to begin transmitting an optical signal. The OPT-AMP card receiver at Node A receives that signal and signals the Node A OPT-AMP card transmitter to resume transmitting.
Note During a laser restart pulse, APR ensures that the laser power does not exceed Class 1 limits. See the “Automatic Power Reduction” section for more information about APR.
13.11.4.5 Scenario 5: Fiber Cut in Nodes Using DCN Extension
Figure 13-30 shows a fiber cut scenario for nodes that do not have OSC connectivity. In the scenario, references to the OPT-BST cards refers to the OPT-BST, OPT-BST-L, OPT-BST-E, OPT-AMP-L, OPT-AMP-C, OPT-AMP-17-C, 40-SMR1-C, and 40-SMR2-C cards when provisioned in OPT-LINE mode.
Figure 13-30 Fiber Cut With DCN Extension
Two photodiodes at Node B monitor the received signal strength for the optical payload. When the fiber is cut, an LOS is detected on the channel photodiode while the other one never gets a signal because the OSC is not present. The AND function then indicates an overall LOS condition, which causes the OPT-BST amplifier transmitter to shut down. This in turn leads to a LOS for the optical payload at
Node A, which causes Node A to turn off the OPT-BST amplifier lasers.
The sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 13-30):
1. Fiber is cut.
2. The Node B power monitoring photodiode detects an LOS on the OPT-BST card. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide for LOS troubleshooting procedures.
3. On the OPT-BST card, the LOS detection triggers a command to shut down the amplifier. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide for alarm troubleshooting procedures.
4. The OPT-BST card amplifier is shut down within one second.
5. The Node A power monitoring photodiode detects a LOS on the OPT-BST card. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide for alarm troubleshooting procedures.
6. On the OPT-BST, the LOS detection triggers a command to shut down the amplifier. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide .
7. The OPT-BST card amplifier is shut down within one second.
When the fiber is repaired, a manual restart with 9 sec restart pulse time (MANUAL RESTART) is required at the Node A OPT-BST transmitter and at the Node B OPT-BST transmitter. A system that has been shut down is reactivated through the use of a 9 sec restart pulse. The pulse indicates that the optical path is restored and transmission can begin.
For example, when the far end, Node B, receives a pulse, it signals to the Node B OPT-BST transmitter to begin transmitting an optical signal. The OPT-BST receiver at Node A receives that signal and signals the Node A OPT-BST transmitter to resume transmitting.
Note During a laser restart pulse, APR ensures that the laser power does not exceed Class 1 limits. See the “Automatic Power Reduction” section for more information about APR.
13.11.4.6 Scenario 6: Fiber Cut in Nodes Using OPT-RAMP-C or OPT-RAMP-CE Cards
Figure 13-31 shows a fiber cut scenario for nodes using OPT-RAMP-C or OPT-RAMP-CE cards.
Figure 13-31 Nodes Using OPT-RAMP-C or OPT-RAMP-CE Cards
The sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 13-31):
1. Fiber is cut in the direction of Node A to Node B.
2. No alarms are initially detected on Node B. The Raman pumps are still in ON state and continue to pump power on to the broken fiber. The residual Raman noise propagated towards the LINE-RX port keeps the embedded EDFA active. The LOS alarm is not raised on the DC-TX port because the EDFA continues to transmit minimum output power to the line amplifier that it is connected to.
3. On Node A, the OPT-RAMP-C card no longer receives the Raman remnant pump signal on the LINE-TX port. The RAMAN-RX port detects an LOS-R alarm on the OPT-RAMP-C or OPT-RAMP-CE card. The OSCM card that is connected to the OPT-RAMP-C card detects OSC failure and raises a LOS alarm at the OC-3 level. For the LOS-R troubleshooting procedures, see the Cisco ONS 15454 DWDM Troubleshooting Guide.
4. On the OPT-RAMP-C or OPT-RAMP-CE card, the LOS-R alarm triggers a command to shut down the Raman pump on Node A.
5. On Node A, the LOS alarm on the OSCM card causes a laser TX shutdown because ALS is always enabled on the OSCM card. This results in the OPT-RAMP-C or OPT-RAMP-CE card raising the LOS-O alarm on the OSC-RX port.
6. Because the Raman pump on Node A is shutdown, the RAMAN-RX port detects an LOS-R alarm on Node B.
7. The LOS-R alarm triggers a command to shut down the Raman pump on Node B.
8. The embedded EDFA on Node B no longer receives residual power Raman noise. An LOS alarm is detected on the input port of the EDFA that causes the embedded EDFA to shut down.
9. The LINE-RX port of the line amplifier on Node B that receives the payload signal from the embedded EDFA of the OPT-RAMP-C card detects an LOS alarm.
10. The LOS alarm triggers an ALS and causes the line amplifier to shut down.
11. The COM-RX port of the OPT-RAMP-C card on Node B and consequently the LINE-TX port that is connected to Node A through the safe fiber, no longer receive power.
12. Because the OSCM card on Node A is in the ALS condition, there is no OSC signal on the LINE-TX port of the OSCM card on Node B that raises an LOS alarm.
13. The LOS alarm on the OSCM card causes a laser TX shutdown that raises an LOS-O alarm on the OSC-RX port of the OPT-RAMP-C card on Node B. The simultaneous presence of an LOS-O alarm on the OSC-RX port and an LOS-R alarm on the RAMAN-RX port of the OPT-RAMP-C card can be interpreted as a fiber cut and an LOS alarm is generated on the LINE-RX port.
14. On Node A, the LINE-RX port of the OPT-RAMP-C card detects an LOS alarm because the C-band payload is absent and triggers a command to shut down the embedded EDFA.
15. The line amplifier that receives the payload signal from the embedded EDFA of the OPT-RAMP-C card detects an LOS alarm on its LINE-RX port and causes the line amplifier to shut down. The C-band power is no longer transmitted to the COM-RX port of the OPT-RAMP-C card and subsequently to the LINE-TX port that connected to the broken fiber.
An Automatic Laser Restart (ALR) on the Raman pump is detected when the fiber is restored. This turns both the Raman pumps to ON state, on both the nodes. When the power on the Raman pump is restored, it turns on the embedded EDFA also. The booster amplifiers on both Node A and Node B detect power on the LINE-RX port. This restarts the booster amplifier.
Once the active TCC of the Raman node detects a stable condition, the link is automatically revaluated. The TCC initiates a fiber restoration procedure as described in Fiber Cut Recovery in Nodes Using OPT-RAMP-C or OPT-RAMP-CE Cards. The procedure takes a maximum of one or two minutes and causes a temporary transient condition on C-band signals.
13.11.4.7 Scenario 7: Fiber Cut in Optical Line Amplifier Nodes Using OPT-RAMP-C or OPT-RAMP-CE Cards
In the following sections, fiber cut scenarios for three node layouts are given:
13.11.4.7.1 Scenario 7A—Node Equipped With OPT-RAMP-C or OPT-RAMP-CE Cards on Side A and Side B.
Figure 13-32 shows a fiber cut scenario for a node equipped with OPT-RAMP-C or OPT-RAMP-CE cards on Side A and Side B.
Figure 13-32 Nodes Using OPT-RAMP-C or OPT-RAMP-CE Cards on Side A and B
The sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 13-32):
1. The fiber that is connected to the LINE-TX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side A of Node A is cut. The Raman link goes down.
2. The RAMAN-RX port detects an LOS-R alarm on the OPT-RAMP-C or OPT-RAMP-CE card on Side A. For LOS-R troubleshooting procedures, see the Cisco ONS 15454 DWDM Troubleshooting Guide.
3. On the OPT-RAMP-C or OPT-RAMP-CE card, the LOS-R alarm triggers a command to shut down the Raman pump on Side A.
4. No power is detected by the embedded EDFA on the LINE-RX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side A.
5. The embedded EDFA of the OPT-RAMP-C or OPT-RAMP-CE card on Side A is automatically shutdown.
6. An LOS-P alarm is detected on the COM-RX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side B of Node A.
7. The LOS-P alarm triggers an ALS of the embedded EDFA of the OPT-RAMP-C or OPT-RAMP-CE card on Side B.
8. No C-band power is transmitted out of the COM-TX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side B, to the COM-RX port and subsequently to the LINE-TX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side A that is connected to the broken fiber.
For information about fiber cut recovery, see the “Fiber Cut Recovery in Nodes Using OPT-RAMP-C or OPT-RAMP-CE Cards” section.
13.11.4.7.2 Scenario 7B—Node Equipped With OPT-RAMP-C or OPT-RAMP-CE and Booster Cards on Side A and OPT-RAMP-C or OPT-RAMP-CE Cards on Side B.
Scenario 1—Fiber cut on the LINE-TX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side A (Figure 13-33).
Figure 13-33 Nodes Using OPT-RAMP-C or OPT-RAMP-CE and Booster Cards on Side A and OPT-RAMP-CE Cards on Side B - Scenario 1
The sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 13-33):
1. The fiber that is connected to the LINE-TX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side A of Node A is cut.The Raman link goes down.
2. The RAMAN-RX port detects an LOS-R alarm on the OPT-RAMP-C or OPT-RAMP-CE card. For LOS-R troubleshooting procedures, see the Cisco ONS 15454 DWDM Troubleshooting Guide.
3. On the OPT-RAMP-C or OPT-RAMP-CE card, the LOS-R alarm triggers a command to shut down the Raman pump on Side A.
4. No power is detected by the embedded EDFA on the LINE-RX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side A.
5. The embedded EDFA of the OPT-RAMP-C or OPT-RAMP-CE card on Side A is automatically shutdown.
6. An LOS alarm is detected on the downstream line amplifier on Side A of Node A since it no longer receives the optical payload from the embedded EDFA of the OPT-RAMP-C or OPT-RAMP-CE card.
7. The ALS mechanism causes the line amplifier to shut down.
8. The C-band power is no longer transmitted out of the line amplifier to the COM-RX port and subsequently to the LINE-TX port of the OPT-RAMP-C or OPT-RAMP-CE card that is connected to the broken fiber.
For information about fiber cut recovery, see the “Fiber Cut Recovery in Nodes Using OPT-RAMP-C or OPT-RAMP-CE Cards” section.
Scenario 2—Fiber cut on the LINE-TX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side B (Figure 13-34).
Figure 13-34 Nodes Using OPT-RAMP-C or OPT-RAMP-CE and Booster Cards on Side A and OPT-RAMP-CE Cards on Side B - Scenario 2
The sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 13-34):
1. The fiber that is connected to the LINE-TX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side B of Node A is cut.
2. An LOS-R alarm is detected on the OPT-RAMP-C or OPT-RAMP-CE card on Side B because it no longer receives the Raman remnant signal from Node B.
3. On the OPT-RAMP-C or OPT-RAMP-CE card, the LOS-R alarm triggers a command to shut down the Raman pump on Side B.
4. The embedded EDFA of the OPT-RAMP-C or OPT-RAMP-CE card on Side B no longer receives residual Raman power and causes it to shut down.
5. A very low C-band signal reaches the OPT-RAMP-C or OPT-RAMP-CE card on Side A. An LOS-P alarm is detected on the COM-RX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side A.
6. The embedded EDFA of the OPT-RAMP-C or OPT-RAMP-CE card on Side A is automatically shutdown.
7. The C-band power is no longer transmitted to the line amplifier through the DC-TX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side A, to the COM-RX port and subsequently to the LINE-TX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side B that is connected to the broken fiber.
For information about fiber cut recovery, see the “Fiber Cut Recovery in Nodes Using OPT-RAMP-C or OPT-RAMP-CE Cards” section.
13.11.4.7.3 Scenario 7C—Node Equipped With OPT-RAMP-C or OPT-RAMP-CE and Booster Cards on Side A and OSC-CSM Cards on Side B.
Scenario 1—Fiber cut on the LINE-TX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side A (Figure 13-35).
Figure 13-35 Nodes Using OPT-RAMP-C or OPT-RAMP-CE and Booster Cards on Side A and OSC-CSM Cards on Side B - Scenario 1
The sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 13-35):
1. The fiber that is connected to the LINE-TX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side A of Node A is cut. The Raman link goes down.
2. The RAMAN-RX port detects an LOS-R alarm on the OPT-RAMP-C or OPT-RAMP-CE card. For LOS-R troubleshooting procedures, see the Cisco ONS 15454 DWDM Troubleshooting Guide.
3. On the OPT-RAMP-C or OPT-RAMP-CE card, the LOS-R alarm triggers a command to shut down the Raman pump on Side A.
4. No power is detected by the embedded EDFA on the LINE-RX port of the OPT-RAMP-C or OPT-RAMP-CE card on Side A.
5. The embedded EDFA of the OPT-RAMP-C or OPT-RAMP-CE card on Side A is automatically shutdown.
6. An LOS alarm is detected on the downstream line amplifier on Side A of Node A because it no longer receives the optical payload from the embedded EDFA of the OPT-RAMP-C or OPT-RAMP-CE card.
7. The ALS mechanism causes the line amplifier to shut down.
8. The C-band power is no longer transmitted out of the line amplifier to the COM-RX port and subsequently to the LINE-TX port of the OPT-RAMP-C or OPT-RAMP-CE card that is connected to the broken fiber on Side A.
For information about fiber cut recovery, see the “Fiber Cut Recovery in Nodes Using OPT-RAMP-C or OPT-RAMP-CE Cards” section.
Scenario 2—Fiber cut on the LINE-RX port of the OSC-CSM card on Side B (Figure 13-36).
Figure 13-36 Nodes Using OPT-RAMP-C or OPT-RAMP-CE and Booster Cards on Side A and OSC-CSM Cards on Side B - Scenario 2
The sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 13-36):
1. The fiber that is connected to the LINE-RX port of the OSC-CSM card on Side B of Node A is cut.
2. An LOS alarm is detected on the OSC-CSM card on Side B because it no longer receives the OSC signal.
3. The power is shut down by means of a 1x1 optical switch in the OSC-CSM card.
Note During a laser restart pulse, APR ensures that the laser power does not exceed Class 1 limits. For more information about APR, see the “Automatic Power Reduction” section.
13.11.4.8 Fiber Cut Recovery in Nodes Using OPT-RAMP-C or OPT-RAMP-CE Cards
A fiber cut recovery procedure is automatically performed after the OCH channels are restored to measure the actual Raman gain on the span.
1. Node A sends a message through OSC or DCN to Node B to be ready for Raman Gain measurement.
2. The TCC configures the Raman pumps on Node A to operate at APR power (+8 dBm). In this state, no Raman amplification is generated on the input fiber of Node A and a reliable span loss measurement is performed. The Raman pumps must not be shut down completely to avoid an improper fiber cut event.
3. Node B acknowledges the message and reports the value of the Raman power received on the channel to Node A.
4. On Node A, the TCC configures the line amplifiers in power control mode and APR state (+8 dBm). The C-band power received with Raman pumps in OFF state is recorded.
5. The TCC turns the Raman pumps to full power maintaining the Raman ratio calculated by the Raman installation wizard. The Raman total power is adjusted, so that the Raman gain setpoint is reached. The actual Raman gain is calculated using the C-band power values.
6. When the Raman gain setpoint is reached, the value of the Power field gets updated and the status of the Fiber Cut Recovery field changes to “Executed” in CTC.
If the provisioned Raman gain setpoint is not reached by setting the Raman total power to the maximum value of 450 mW, the procedure stops and the RAMAN-G-NOT-REACHED alarm is raised on the OPT-RAMP-C or OPT-RAMP-CE card.
13.11.5 Network Optical Safety on RAMAN-CTP and RAMAN-COP Cards
Bidirectional optical safety mechanisms for Raman and C-band signals have been independently implemented. The Raman pump laser shutdown and restart is managed by the RAMAN-CTP card. The RAMAN-COP card is controlled by the RAMAN-CTP card using two backplane wires. The RAMAN-COP card can be absent in some node configurations.
The C-band signal shutdown and restart is managed by an MSTP card, such as 40-SMR1-C, 40-SMR-2C, OPT-EDFA-17, or OPT-EDFA-24.
The optical safety mechanism on the RAMAN-CTP and RAMAN-COP cards is managed by:
- DFB signal (1568.77 nm) and detection of DFB related signals—The RAMAN-CTP card on the local node transmits a DFB signal and waits for a similar response from the remote side. If a valid DFB signal is not detected, the RAMAN-CTP card switches off its transmitting DFB laser that causes a loss of DFB signal on the remote RAMAN-CTP card which in turn switches off its DFB laser. Both the RAMAN-CTP cards must turn off the DFB signals, when a fiber cut occurs.
- Raman pump laser back reflection mechanism on the RAMAN-CTP and RAMAN-COP cards—This mechanism uses the ratio between the back-reflected optical power and the total output Raman pump power to reduce the output power when patchcords are removed. If excessive back-reflection occurs, a Raman Laser Shutdown (RLS) alarm is raised on the RAMAN port where the failure is detected.
- Photodiode (P8) on the RAMAN-CTP card—The photodiode (P8) detects the Raman pump power transmitted by the RAMAN-COP card and is used to check for optical continuity between the RAMAN-CTP and RAMAN-COP cards. The RAMAN-COP card is shut down if the cards get disconnected.