Terminology » Fiber Optic » ROADM Types: WB vs PLC vs WSS vs WXC

ROADM Types: WB vs PLC vs WSS vs WXC

roadm fiber optic optical network wavelength optical component

This page compares different types of ROADMs: WB, PLC, WSS, and WXC. It highlights the differences between WB (Wavelength Blocker), PLC (Planar Lightwave Circuit), WSS (Wavelength Selective Switch), and WXC (Wavelength Crossconnect) ROADM types. ROADM stands for Reconfigurable Optical Add Drop Multiplexer. All the ROADM types mentioned here are used as reconfigurable add/drop multiplexers in the fiber optic domain.

WB-Wavelength Blocker ROADM

WB ROADM configuration

Figure-1 depicts configuration of WB ROADM type.

PLC-Planar Lightwave Circuit ROADM

PLC ROADM configuration

Figure-2 depicts configuration of PLC ROADM type.

WSS-Wavelength Selective Switch ROADM

WSS ROADM configuration

Figure-3 depicts configuration of WSS ROADM type.

WXC-Wavelength Crossconnect ROADM

WXC ROADM configuration

Figure-4 depicts configuration of WXC ROADM type.

Comparison Table of ROADM Types

The following table summarizes the differences between the ROADM types discussed above.

Comparison FactorWB ROADMPLC ROADMWSS ROADMWXC ROADM
Full FormWavelength BlockerPlanar Lightwave CircuitWavelength Selective SwitchWavelength Crossconnect
Configuration2 DWDM ports e.g. 1 IN and 1 OUT2 DWDM ports e.g. 1 IN, 1 OUT and 2*N single λ portsN+1 DWDM ports e.g. 1 IN, 1 OUT and N-1 service2*N DWDM ports e.g. N-1 IN, N-1 OUT, 1 ADD and 1 DROP
Sub-systemLCD WBPLCsmall switch array and AWGs (Arrayed Waveguide Grating)1 x N MEMS WSS, 1 x N LCD WSS, 1 x N LCoS WSS PLC Matrix Switches and AWGs
Advantages (Pros)It is first ROADM developed, Number of A/D ports = N (All λ’s)• low power consumption
• Lowest cost
• No moving parts
• No vibration sensitivity		• Can be mesh upgradable
• Can be colorless
• Lowest cost for degree 5 to 8		• Upgradable to any degree as per internal architecture
• Any multiple λ’s between any two ports
Disadvantages (Cons)• Not mesh upgradable
• Supports DCE function only		• extra optical devices such as splitters, combiners, taps are needed for A/D
• Not easily upgradable to Degree-2, • Not easily colorless		• Vibration sensitive
• Not cost effective for degree-2 version
• Number of A/D ports are less than N and not λ upgradable		Costly if non PLC switches, MUX, De-mux are used.