Compact Reverse Transmitters with DFB or CWDM Lasers Data Sheet

Cisco^® Compact Nodes can be configured with a variety of optical reverse transmitters to provide flexibility for use in multiple applications. These reverse transmitters are plug-in modules that deliver a cost-effective, user-friendly solution for upstream transmission. The Compact Reverse Transmitters (Figure 1) are available with distributed feedback (DFB) or Coarse Wavelength Division Multiplexing (CWDM) lasers.

All transmitters feature a built-in microprocessor and pilot tone for easy set-up of the reverse path. The pilot tone does not take up any reverse bandwidth as it is placed at 5 MHz. Moreover, placing the pilot tone at 5 MHz also makes the reverse transmitter interoperable with virtually all reverse receivers in the marketplace. If there is no modulation, the pilot tone serves as a quieting tone, which reduces spurious noise and improves overall noise performance with up to 15 dB. All reverse transmitters have increased gain, which allows low reverse input levels at the node.

The reverse transmitter can also run in burst mode which makes it possible to deploy Cisco Compact Nodes in a radio frequency over glass (RFOG) network.

Reverse Transmitters and CWDM

The reverse transmitters (Figure 2) are an integral part of the CWDM transport system making it possible for each fiber in a hybrid fiber-coaxial (HFC) network to support a sixteen-fold increase in the number of wavelengths available. The CWDM lasers offer two output powers, 3 dBm and 6 dBm.

General Features

●   Designed to operate within the Cisco Compact Nodes (A90100/A90300, A90200, A90201)

●   Variable modulation depth (RF drive level) promotes superior link optimization

●   RF input test point

●   5-MHz pilot tone for easy setup

●   Multiple setup and control options

◦     Local control with front panel or Cisco Handheld Programmer Terminal Model 91200

◦     Advanced element management (status monitoring and control) interface

●   Nonvolatile storage of preset operating parameters

●   Remote optical modulation index (OMI) setting, when supported by node

●   Burst mode for interoperability in RFoG

●   0 dBm DFB

●   3 dBm and 6 dBm, DFB available in 16 CWDM wavelengths

●   Uncooled DFB lasers with Isolator for exceptional performance and low power consumption

Noise Power Ratio (NPR) Performance

Figures 3 through 5 show the NPR performance of the Compact Reverse Transmitter.

Test condition: Prisma^® II Reverse Optical Receiver (part number: P2-RRX-STD), 10 dB optic link (20 km glass, plus passive loss), Cisco Compact EGC Fiber Deep Node A90100 in default setting, with reverse transmitter attenuator at 10dB and room temperature.

Node Correction Factor

A Cisco A90100 Node is used in the NPR tests in figures 3 through 5. For the nodes listed in Table 1, the X-axis in the three figures, which indicates input power per hertz, must move to the left by the correction factor also listed in Table 1. The node is set to its default configuration and tested with a reverse jumper in the diplexer slot.

Table 1.       Node Correction Factor

Example: Node type A90200 has a correction factor of –2.2 dB. From the NPR-curve (Figure 3), a 0 dBm DFB laser (part number: CMPT-RTX-0-13) will have the best NPR performance (47.5dB) at an input of –53 dBmV/Hz. For Node type A90200 the required input power at the port will need to increase to –50.8 dBmV/Hz (= -53 – (–2.2)) to achieve the best NPR performance.

NPR Performance Descriptions

The NPR performance plots contained in this document depict the NPR performance on a reference 10 dB fiber optic link.

With other link losses, the following items vary from that shown on the reference 10 dB link plots.

●   NPR dynamic range for a given minimum NPR performance (Carrier to Noise ratio)

●   NPR value for a given transmitter RF input level

To determine an NPR dynamic range for a different link loss: Add (or subtract) the correction factor from Table 2. Associated with the desired link loss to (or from) the dynamic range shown on the reference 10 dB link NPR plots. Note that the associated increase (or decrease) in dynamic range affects only the left side of the NPR curve (minimum RF input side), since that is the portion of the curve affected by changes to the traditional noise sources associated with optical link.

To determine an NPR value for a different link loss: Add (or subtract) the correction factor from Table 2 associated with the desired link loss to (or from) the NPR value shown on the 10 dB link NPR plot for a given RF input level. Again, only the NPR values on the left side of the NPR curve (prepeak values) are to be adjusted. The NPR values and slope associated with the right side of the NPR curve (post peak values) are primarily due to laser clipping at high RF input levels. Therefore, they do not vary appreciably with link loss, but only with the channel load.

Table 2 lists link loss correction factors.

Table 2.       Link Loss Correction Factors for 5 to 65 MHz

Table 3.       Link Loss Correction Factors for 5 to 204 MHz

Example: Figure 6 shows how dynamic range (for NPR of 30 dB) of a 0 dBm DFB-laser will be influenced for 6 dB link loss and 15 dB link loss for 5 to 65 MHz.

Product Specifications

This section lists product specifications for.

Table 4.       Specifications

Ordering Information

Table 5 lists ordering information for reverse transmitters. Table 6 provides ordering information for required accessories, which must be ordered separately.

To place an order, visit the Cisco Ordering Home Page.

Table 5.       Ordering Information

Table 6.       Required Accessories

Cisco Capital

Financing to Help You Achieve Your Objectives

Cisco Capital can help you acquire the technology you need to achieve your objectives and stay competitive. We can help you reduce CapEx. Accelerate your growth. Optimize your investment dollars and ROI. Cisco Capital financing gives you flexibility in acquiring hardware, software, services, and complementary third-party equipment. And there’s just one predictable payment. Cisco Capital is available in more than 100 countries. Learn more.

For More Information

To learn more about Cisco Compact Reverse Transmitters, visit: http://www.cisco.com/c/en/us/products/video/compact-nodes/index.html