Have an account?

  •   Personalized content
  •   Your products and support

Need an account?

Create an account

Cisco 1.2 GHz GS7000 Remote PHY Module Compatible 2X2 Segmentable Node Installation and Configuration Guide

Book Contents
Find Matches in This Book
Available Languages
Download Options

Book Title

Cisco 1.2 GHz GS7000 Remote PHY Module Compatible 2X2 Segmentable Node Installation and Configuration Guide

Chapter Title

Theory of Operation

Results

Updated:
February 24, 2019

Chapter: Theory of Operation

Theory of Operation

This chapter describes the theory of operation for the 1.2 GHz GS7000 Remote PHY Device (RPD) 2X2 Segmentable Node, including functional descriptions of each module in the node.

System Diagrams

1x4 FCM and 4x1 RCM with RPD Module

The following diagrams show the signal flow for the node with RPD 1x4 Forward Configuration Module and RPD 4x1 Reverse Configuration Module.


Note

Dash line means the module is not installed.

1x4 FCM Analog and 4x1 RCM with Analog Optics

The following diagrams show the signal flow for the node with RPD 1x4 Forward Configuration Module Analog Only Configuration and RPD 4x1 Reverse Configuration Module.


Note

Dash line means the module is not installed.

1x4 FCM and 4x2 RCM with RPD Module

The following diagrams show the signal flow for the node with RPD 1x4 Forward Configuration Module and RPD 4x2 Reverse Configuration Module.


Note

Dash line means the module is not installed.

1x4 FCM Analog and 4x2 RCM with Analog Optics

The following diagrams show the signal flow for the node with RPD 1x4 Forward Configuration Module Analog Only Configuration and RPD 4x2 Reverse Configuration Module.


Note

Dash line means the module is not installed.

2x4 FCM and 4x2 RCM with RPD Module

The following diagrams show the signal flow for the node with RPD 2x4 Forward Configuration Module and RPD 4x2 Reverse Configuration Module.


Note

Dash line means the module is not installed.

2x4 FCM Overlay and 4x1 RCM with RPD and Overlay

The following diagrams show the signal flow for the node with RPD 2x4 Forward Configuration Module Overlay and RPD 4x1 Reverse Configuration Module.


Note

Dash line means the module is not installed.

Forward Path

Forward path refers to signals received by the node from the hub or headend. These signals are amplified in the node and routed to subscribers through the cable distribution network.

Forward Path Signal Routing

The 1.2 GHz GS7000 Remote PHY Device (RPD) 2X2 Segmentable Node 4-way forward path signal routing functions are described below.

Stage

Description

1

1310 nm or 1550 nm optical signals from the headend are applied to receiver module 1 and/or RPD module in the node.

2

The receiver module detects the signal on the optical carrier applied to it and outputs an electrical RF signal to the node Optical Interface Board (OIB). Receiver can be used as the sole source of forward signals or as an overlay source to 550MHz to supplement the RPD. RPD 1x2 or 2x2 can be the source for forward path signals and can be used in conjunction with the analog RX for overlay.

3

The RF signals travel across the OIB and cables to the Forward Configuration Module (FCM). The FCM determines how RF signals from the different modules are routed to the four independent forward amplification paths in the RF amplifier module. The FCM routes the RF signals entering it between the four forward amplification paths in the RF amplifier module.

4

Each of the forward amplification paths in the RF amplifier module is composed of one input amplification stage and one interstage amplification stages in series followed by a power doubler output amplification stage. This topology provides one driven output port for each of the forward amplification paths in the RF amplifier module, for a total of four driven node output ports.

5

Each of the forward amplification paths in the RF amplifier module also contains padding, trimming, thermal compensation, equalization, and filtering circuitry.

6

Node signal directors are present at two of the nodes forward output ports and allow the signals at those ports to be redirected to the nodes auxiliary output ports or split equally between the primary and auxiliary node output ports. In this way, the node can be configured to have up to six output ports.

Reverse Path

Reverse path refers to signals received by the node from the cable distribution network. These signals are amplified in the node and returned to the headend optically through the fiber portion of the network. The reverse path is not used in all networks.

Reverse Path Signal Routing

The node’s reverse path signal routing functions are described below.

Stage

Description

1

Reverse path RF signals are applied to node RF ports 1, 2, 4, and 5.

2

The RF signals from each of the four node RF ports are amplified independently in the RF amplifier module and routed to the Reverse Configuration Module (RCM).

3

Each of the reverse amplification paths in the RF amplifier module also contains padding, trimming, filtering, -6 db wink, and RF On/Off switch circuitry.

4

The RCM determines how RF signals from the different node output ports are combined and routed to the two RPD or transmitter module paths on the Optical Interface Board (OIB). The RCM combines the reverse path signals from the 6 node output ports together and directs them to the transmitter module and /or RPD US path on the OIB.

5

The RF signals travel across the OIB to transmitter module and/or RPD. The transmitter modulates the RF signals entering it onto an optical carrier and routes it through the fiber portion of the network back to the headend. RPD routes DOCSIS traffic.

Power Distribution

The node is powered by one or two power supplies.

The node’s power distribution functions are described below.

Stage

Description

1

45 to 90 V AC is applied to one or two power supply modules in the node.

2

The power supply module(s) convert(s) the AC input to +24.5, +8.5, -6.0, and +5.5 V DC.

3

The +24.5, +8.5, -6.0, and +5.5 V DC lines are routed to node internal modules.

4

If two power supplies are installed and both are active, the load is shared equally between them.

5

An AC segmentable shunt is available to separate the AC connection to ports 1-3 from that of ports 4-6. This allows the node to be configured where one power supply is powered from ports 1-3 and a second power supply is powered from ports 4-6.

RF Amplifier Module

This section describes the RF amplifier module. The RF amplifier module contains the forward band and the reverse band amplifiers.

Functional Diagrams

The following diagrams show how the RF amplifier functions.

Figure 1. Forward Amplifier
Figure 2. Reverse Amplifier and OIB

Forward Band Amplification 4-Way Path Description

The RF amplifier module provides all forward signal amplification outside the optical receiver or RPD module in the GS7000 Node.

The segmentable launch amplifier contains four independent forward amplification paths, each having one input near the center of the amplifier module and one, two or three outputs at one end of the amplifier module. Each of the forward paths is comprised of the forward configuration module, an input gain block, a frequency response trim circuit, a thermal compensation circuit, an inter-stage pad, a 2-way splitter or RF switch circuit, an inter-stage gain block, a plug-in forward band linear equalizer, an output pad, an output gain block, a diplex filter, a bi-directional 20 dB down forward test point, and finally an AC bypass circuit.

The thermal circuit on the RF amplifier module is designed to compensate for the RF forward path thermal movement of the entire node RF station. This includes the forward path amplifier module circuitry, RF cables, and optical interface board circuitry. It does not include the thermal movement of the optical receivers or RPD.

Forward Configuration Module

The forward configuration module determines the forward path topology in the RF amplifier module and the node. The output signals from one receiver and/or RPD enter the forward configuration module where they are combined and/or directed to the two independent forward paths in the RF amplifier module. Forward path segmentation and/or redundancy are set by plugging the appropriate forward configuration module into the RF amplifier module. The forward configuration module is a plug-in, field accessible module. See Forward Configuration Module for more information.

Forward Band Linear Equalizer Module

The forward band linear equalizer module sets the overall forward path tilt of the RF amplifier module and the node. The 1.2GHz GS7000 Node launch amplifier is shipped with four 18.0 dB linear equalizers installed in the RF amplifier module. One equalizer is installed in each of the four amplifier module forward paths. This sets the nodes forward path tilt to 17.5 dB linear. Forward band linear equalizer modules of other values are available. This allows the nodes forward path tilt to be adjusted as needed. The forward band linear equalizer module is a plug-in, field accessible module. See Forward Equalizer Chart.

Node Signal Director Jumper/Splitter Module

The node signal director jumper/splitter module is a plug-in, field accessible module. It is present on the center output ports on either end of the RF amplifier module. The orientation of these modules determines where the RF amplifiers center output port signals are directed. The node signal director jumper allows the center output port signals to be routed to either the amplifiers primary center output port or to its auxiliary corner output port. The node signal director splitter module splits the center output port signals equally between the primary and auxiliary output ports.

Reverse Band Amplification Path Description

The RF amplifier module provides all reverse signal amplification outside the optical transmitter and RPD module in the node. It contains four independent reverse paths comprised of an AC bypass circuit, a bi-directional 20 dB down reverse test point, a diplex filter, an input pad, a low pass filter, a 6 dB switched attenuator, a 16 dB gain block, a second low pass filter, an RF on/off switch, a frequency response trim circuit, and a reverse configuration module. The 6 dB switched attenuator and RF on/off switch circuits allow each reverse path to have 6 dB (wink) and on/off capabilities. These circuits are controllable from the headend via the status monitor or locally via the local control module and a hand held controller. A serial communication link is provided between status monitor or local control module and the reverse band launch amplifier. Circuitry on the amplifier converts the serial communications to parallel control signals and routes them as needed.

Reverse Configuration Module

The reverse configuration module determines the reverse path topology in the RF amplifier module and node. The input signals from four independent amplifier module output ports enter the reverse configuration module where they are combined and/or directed to one to two optical transmitters or RPD US path. Reverse path segmentation and or redundancy is set by plugging the appropriate reverse configuration module into the RF amplifier module. The reverse configuration module is a plug-in, field accessible module. See Reverse Configuration Module for more information.

Forward Configuration Module

The forward configuration module determines the forward path topology in the RF amplifier module and the node. The output signals from one optical receiver and/or RPD module enter the forward configuration module where they are combined or directed to the four independent forward paths in the RF amplifier module. The various types of the forward configuration module are described below.

RPD 1x4 Forward Configuration Module Description

The RPD 1x4 Forward Configuration Module is used when the node is configured with a 1X2 RPD module. This FCM routes a single downstream signal to all four RF ports of the node. This module splits the signals equally to the inputs of the node.

The following diagram shows how this module functions.

RPD 1x4 Forward Configuration Module with Overlay Description

The RPD 1x4 Forward Configuration Module with Overlay is used when the node is configured with a 1X2 RPD module and a single analog overlay optical receiver. The signal of the RPD module and receiver are combined and routed to all four RF ports of the node. In this overlay configuration a low pass filter is inserted in the OIB RCVR1 Attenuator location. Attenuator/Filters are available in 1 dB increments and limit the overlay path to 550MHz.

The following diagram shows how this module functions.

RPD 1x4 Forward Configuration Module Analog Only Description

The RPD 1x4 Forward Configuration Module Analog Only is used with a single standard GS7000 Node receiver when an RPD module is not used in the node. This FCM will route the forward signal to all node RF ports.

The following diagram shows how this module functions.

RPD 2x4 Forward Configuration Module Description

The RPD 2x4 Forward Configuration Module is used when the node is configured with a 2X2 RPD module. The two segmented outputs of the RPD module are routed to opposite sides of the launch amplifier. One RPD output provides the downstream signal for RF ports 1-3 of the node and the other RPD output provides signal to RF ports 4-6 of the node.

The following diagram shows how this module functions.

RPD 2x4 Forward Configuration Module with Analog Overlay Description

The RPD 2x4 Forward Configuration Module with Analog Overlay is used when the GS7000 Node is configured with a 2X2 RPD module and an analog overlay receiver. In this configuration, the RPD has two segmented outputs which are routed to opposite sides of the launch amplifier and both signals are combined with the signal from the receiver as well. One RPD output combined with the receiver provides the downstream signal for RF ports 1-3 of the node and the other RPD output combined with receiver signal provides signal to RF ports 4-6 of the node.

The following diagram shows how this module functions.

Reverse Configuration Module

The reverse configuration module determines the reverse path topology in the RF amplifier module and node. The input signals from four independent amplifier module output ports enter the reverse configuration module where they are combined and/or directed to optical transmitters and/or RPD US. The two RPD compatible reverse configuration modules are described below.

RPD 4x1 Reverse Configuration Module Description

The RPD 4x1 Reverse Configuration Module can be used with either a 1X2 RPD or 2X2 RPD. This RCM can also be used in nodes without an RPD module. In this configuration, either an analog or EDR transmitter should be used. This RCM combines the signal from all 4 node RF ports to be routed to either the RPD module and/or transmitter.


Note

This module has 2 redundant copies of upstream signals and if an output is unused, it should be terminated in the OIB.

The following diagram shows how this module functions.

RPD 4x2 Reverse Configuration Module Description

The RPD 4x2 Reverse Configuration Module can be used with either a 1x2 or 2X2 RPD module or a 2:1 EDR transmitter, or 2 analog transmitters, or 2 1:1 EDR transmitters. The transmitters should be used in a configuration where an RPD module is not used. This RCM combines reverse inputs from ports 1 and 2/3 and routes them to either RPD input 2 or Transmitter 2 on the OIB; it also combines reverse inputs from ports 4 and 5/6 and routes them to either RPD input 1 or Transmitter 1 on the OIB.

The following diagram shows how this module functions.

Optical Interface Board

The Optical Interface Board (OIB) provides all interconnections between the modules in the housing lid of the node. The modules in the housing lid can include the RPD, optical receiver, optical transmitter, power supply, and status monitoring/local control modules. Each module in the lid plugs directly into the OIB through a connector header or row of sockets. Input attenuator pads are provided on the OIB for the optical receiver in the housing lid. Output attenuator pads are provided on the OIB for optical transmitter or RPD. All RF and power cables running between the housing lid and base also plug into the OIB.

The OIB is field replaceable. All modules, power supplies, RF cables, power cables, and OIB mounting screws must be removed in order to remove the OIB from the housing lid.

The upstream status monitoring signal goes through LPF then splits. Splitter output 1 goes through a 17dB coupler into transmitter 1 input. Splitter output 2 goes through a plug-in attenuator pad, a 17dB coupler and into transmitter 2 input.

The purpose of the attenuator Tx2 SM Term is to terminate the upstream status monitoring signal going into transmitter 2 when either the node is segmented or EDR transmitter is in use. When the node is configured in EDR mode, a 75 dB pad must be placed in the Tx2 SM Term.

Optical Receiver Module

The optical receiver module takes in optical signals and puts out forward band RF signals. The module cover has a sliding tray incorporated into it allowing the receivers fiber pigtail to be spooled up and contained within the receiver module. This greatly improves fiber management within the node.

The optical receiver module plugs directly into the optical interface board via a connector header and is secured in place with two screws. An input attenuator pad is provided on the optical interface board for the receiver mounted in the housing lid.

All optical receiver test points are provided and are accessible through holes in the module housing. The optical power test points for the optical receiver module has a scaling ratio of 1 V = 1 mW. A -20 dB RF power test point is accessible through the front panel.

The optical receiver module has an optical power LED to indicate the presence of optical power that is either above or below the specified range. ON indicates optical power is within operating limits and OFF indicates that optical power is below the alarm threshold.

Figure 3. Optical Receiver Module

The optical power level into the optical receiver module is monitored by the status monitor or local control module.

The following diagram shows how the optical receiver module functions.

Figure 4. Optical Receiver Module Diagram

There are two types of the receiver module: Standard Input Optical Receiver and Low Input Optical Receiver.

Figure 5. Standard and Low Input Optical Receiver

The optical input range for the low input receiver is 0.1 w to 0.63 w (-10 dBm to -2 dBm). Compared to the standard input optical receiver (the optical input range is -6 dBm to +2 dBm (0.25 w to 1.58 w)), the low input optical receiver can work with lower optical input level, in order to support fiber deep applications.

The illustration below is Low Input Receiver RF Output Level and Transmitter OMI: Rx Switch in 0 dB Setting:

The illustration below is Low Input Receiver RF Output Level and Transmitter OMI: Rx Switch in -8 dB Setting:

For the detailed information about the low input optical receiver, please refer to the latest GS7000 Data Sheet.

Optical Analog Transmitter Module

The optical analog transmitter module takes in reverse band RF signals and puts out optical signals. The node is designed to work specifically with the existing mid gain, temperature compensated DFB optical transmitters. Other mid and high gain optical transmitters may be installed in the node with varying effects on the overall node specifications. The new module cover fits on all existing optical transmitters. This module cover has a sliding tray incorporated into it allowing the transmitters fiber pigtail to be spooled up and contained within the transmitter module. This greatly improves fiber management within the node.

The optical transmitter module plugs directly into the optical interface board via a connector header and are secured in place with two screws. Output attenuator pad is provided on the optical interface board for each transmitter mounted in the housing lid.

RF test points are accessible through holes in the module housing. The optical power test point for the optical transmitter module has a scaling ratio of 1 V = 1 mW. A -20 dB RF power test point is accessible through the module top cover.

The top cover contains a status monitor LED. Each optical transmitter module laser power indicator turns off when the laser power output falls outside the alarm threshold. It is on (green) when within the alarm threshold.

Figure 6. Optical Analog Transmitter Module

The following diagram shows how the optical analog transmitter module functions.

Figure 7. Optical Analog Transmitter Module Diagram

Local Control Module

A local control module and a status monitor are available for the node. A status monitor consists of a local control module with a transponder core module installed in the housing. The same housing is used for both units. The units perform the following function:

  • Local Control Module – reverse path troubleshooting

  • Status Monitor - adds status monitoring capability to the local control module

  • DOCSIS capability

Status Monitor Description


Note

It is impossible to use RPD module and status monitor in one node.

The status monitor is DOCSIS compliant and provides node monitoring and control capability at the cable plant's headend. The following node voltages and signals are monitored and their status reported to the headend by the status monitor.

  • Receiver optical input level

  • Transmitter optical output level (all transmitters)

  • AC power presence and peak voltage (for split AC powering cases, AC power from both sides of node housing is monitored)

  • DC voltages from both primary and redundant power supplies

Commands are sent from the headend to the status monitor. The status monitor communicates serially with the RF amplifier module, the reverse band 6 dB (wink) attenuators on the reverse amplifier PWB, and the reverse band on/off switches on the reverse amplifier PWB.


Note

Configuration parameters for the transponder core module, such as IP address, can be changed using the PC-based GS7000 ViewPort software.

Figure 8. Status Monitor

Note

The transponder core module can be seen through the Heart Beat/Receive/Error indicator cutout in the cover.

Local Control Module Description

The local control module locally monitors the following node voltages and signals:

  • Receiver optical input level

  • Transmitter optical output level (all transmitters)

  • AC power presence and peak voltage (for split AC powering cases, AC power from both sides of node housing is monitored)

  • DC voltages from both primary and redundant power supplies

The local control module is equipped with a USB port to allow local control of the optional forward band redundancy switches, the reverse band 6 dB (wink) attenuators, the reverse band on/off switches, through the PC-based GS7000 ViewPort software. All parameters monitored by the local control module can be displayed and reviewed using ViewPort.

Figure 9. Local Control Module

Note

The local control module can be upgraded to a status monitor through the addition of a transponder core module. The transponder core module plugs directly onto the local control module’s PWB. The mechanical housing for the status monitor and the local control module are the same. The Heart Beat, Receive, and Error indicator LEDs are only present if the transponder module is installed.

Power Supply Module

The power supply module converts a quasi-square wave, 50 – 60 Hz AC input voltage into four well-regulated DC output voltages. The supply is an off-line, switched-mode power supply with a large operating range. This reduces service outages by converting long duration AC surges into load power. The power supply is a constant power device, meaning that it automatically adjusts its internal operating parameters for the most efficient use of the different levels of input voltage and current it will receive within the cable plant.

The DC output voltages generated by the power supply, at given load currents, are shown below:

  • +24.5 VDC @ 6.2 Amps

  • +8.5 VDC @ 1.0 Amps

  • +5.5 VDC @ 1.3 Amps

  • -6.0 VDC @ 0.8 Amps

Test points are provided on top of the power supply module for AC input and all output DC voltage rails.

The power supply module plugs directly into the optical interface board, no external cables are required.

A node can be configured with one or two power supplies. AC input voltage can be routed to both power supplies commonly from any node output port. In addition, AC input voltages can be routed in a split fashion to the two power supplies. AC input voltages from the left half of the node (output ports 1 – 3) can be routed to power supply 1 independent of AC input voltages from the right half of the node (output ports 4 – 6) being routed to power supply 2. Each of the power supplies output voltage rails is diode OR'd within the supply. This creates common DC powering circuits when multiple supplies are present in the node.

Node Power Limitations

The node must be configured in a manner that prevents potential thermal overloads. Heat generated by the node can reduce the life of the equipment.


Caution

The life of the equipment may be reduced if configured to draw more than the recommended level of power from the power supplies.

Two power supplies can provide a maximum power level of 155 watts to the node. The RF amplifier uses the majority of the available power. Maintain the total power consumption of all modules in the housing within these guidelines to minimize the heat generated. Find the optimal configuration by summing the power consumption of the RF amplifier plus the other individual modules in the housing using the following table.


Important

Do not populate the housing with any combination of modules that would draw more than the available power of 155 watts.

The following table lists the modules and their respective electrical parameters.

Equipment Type Maximum Power Draw (Watts) Typical Power Draw (Watts)
Transmitter 1310 nm dfb, analog CWDM 4.1 3.4
Transmitter analog DWDM 5.4 4.8
Standard Input Receiver operating 4.1 3.9
Standard Input Receiver standby 0.5 0.4
Low Input Receiver operating 4.1 3.85
Low Input Receiver standby 0.5 0.4
1x2 RPD 48
2x2 RPD 55
Status Monitor/ Local Control Module 2.6 0.9
RF Amplifier 4-way forward segmentable 72.8 72.9
1:1 EDR Transmitter < 3
2:1 EDR Transmitter < 7

Was this Document Helpful?

FeedbackFeedback

Contact Cisco

Related Cisco Community Discussions

About Us
Contact Us
Work with Us