Understanding the Integrated Photonic Line Card Architecture

Architecture Overview

You can use the integrated photonic line system to transport 100 Gbps coherent DWDM optics located in either the same or different PTX3000 chassis, a PTX5000 chassis, or an MX Series chassis—simply make the proper physical connections between the ADD and DROP ports on the IPLC module and the interface in the chassis. All connections between the DWDM optics and the IPLC are made through the front panel. The IPLC base module accepts and then multiplexes 32 individual wavelengths (connected through the ADD and DROP ports on the front panel) into a single fiber pair. If you require more than 32 channels, you can connect the optional IPLC expansion module to the IPLC base module to increase the port capacity of the node to 64 ports.

The wavelengths from the ADD and DROP ports are then amplified, monitored, and controlled and then transmitted towards the optical network over the Line OUT port on front panel of the IPLC base module. In the reverse direction, the received signals from the optical network on the Line IN port are amplified to overcome for loss in the optical fiber and then demultiplexed into individual wavelengths and sent to the configured ADD and DROP ports on the front panel.

The 32 channels provided by the IPLC base module are known as the odd channels. The 32 channels provided by the optional IPLC expansion module are known as the even channels. This odd and even designation reflects the default wavelengths the channels support.

In the multiplexing-add path, the 32 even channels from the IPLC expansion module are interleaved with the 32 odd channels from the IPLC base module. In the demultiplexing-drop path, the 32 even channels are separated from the odd channels using a deinterleaver. All 64 channels go through the main common components used for amplification and equalization. All 32 channels on the IPLC base module are 100 GHz spaced, per the ITU-T Grid Specifications (G.694.1). The 32 channels on the IPLC expansion module are offset from the IPLC base module channels by 50 GHz.

Two-Degree Node

For ring topologies and other network topologies that require a two-degree node for east-and west communications, you can connect two IPLC base modules together through the PT IN-PT OUT ports on the front panel and enter a few CLI commands to form a two-degree node. Two-degree nodes enable you to route wavelengths in both directions.

Functional Component Overview

The high-level optical functional block diagram of the combined functions of both the IPLC base module and the IPLC expansion module are shown in Figure 1.

Figure 1: Combined Functions of the IPLC Base and Expansion Modules

IPLC Base Module Functional Components

The main building blocks of the IPLC base module architecture are as follows:

• A 2x1 wavelength selective switch (WSS) on the add path selects wavelengths from among all channels presented from the 32 Add ports of the IPLC base module (shown in blue in Figure 1) and from the 32 Add ports on the IPLC expansion module (shown in gray in Figure 1).

• A booster erbium-doped fiber amplifier (EDFA) (E1) followed by a variable optical attenuator (VOA) compensate for the loss of the WSS, multiplexer, and 3 dB coupler.

• A variable gain preamplifier EDFA (E2) to compensate for the loss of the preceding fiber span.

• An optical channel monitor (OCM) with three points of observation including the following:

  • Booster EDFA (E1) output

  • Preamplifier EDFA (E2) output

  • The combined channels of the local add function at the input of the WSS, which indicates which channels (both odd and even channels) are being added locally

  • An optical supervisory channel (OSC) communicates inband with the remote IPLC modules, as well as the optical ILA and is used for the analysis of the fiber span characteristics, performance monitoring, and IPLC fault handing.

  • An optical splitter is used to broadcast the received signal from the output of the preamplifier (E2) toward both DROP and PT IN and PT OUT ports

  • Four power monitors:

    • AWG Add—Monitors the input of the WSS measuring the total input power of the combined channels of the local add function

    • Express In—Monitors the input of the WSS measuring the total input power at the input to the WSS coming from the PT IN and PT OUT express ports

    • Line IN—Monitors the input at the Line IN port, for detection of the incoming line signal optical power

    • Line OUT—Monitors the output at the Line OUT port, for detection of the outgoing line signal optical power

    • OSC ADD—Monitors OSC power at Line OUT

    • OSC DROP—Monitors OSC power at Line IN

IPLC Expansion Module Functional Components

The IPLC expansion module is a passive multiplexer/demultiplexer that interfaces only with the IPLC base module. The IPLC expansion module receives its sole input from and delivers its sole output to the IPLC base module through the XPN IN and XPN OUT ports. As such, it does not interface directly with the network or the high-speed backplane of the PTX3000 Series router. Figure 1 shows the main building blocks for both the IPLC base module and expansion module, which include:

• Add filter capable of multiplexing 32 DWDM channels of certain wavelengths

• Drop filter capable of demultiplexing 32 DWDM channels having the same certain wavelengths

• Demultiplexing filter whose input (which is also the sole input to the expansion module) is monitored through a power detector. The power detector determines whether light is present. If light is present, the power detector determines whether the light has reached the expansion module through the patch cord between the IPLC base module and the IPLC expansion module.