optical performance monitoring solutions for the networks of today and tomorrow

The introduction of reconfigurable optical add-drop multiplexers (ROADMs) is driving the requirement for optical performance monitoring of channels in optical communication networks. A key monitoring parameter is optical signal-to-noise ratio (OSNR), which is traditionally estimated by linear interpolation of the amplified spontaneous emission (ASE) noise measured between WDM channels. This “out of band” technique is no longer valid in reconfigurable networks, since the optical filtering in the ROADMs removes the noise between the channels. Instead, in-band monitoring techniques are essential to measure the actual OSNR. 

Requirements for a practical OSNR monitor include low cost, low power requirements, insensitivity to other impairments and format/bit rate independence.  We have developed a simple, robust solution to directly monitor the OSNR within the optical channel bandwidth, where it really matters.

The current deployment of reconfigurable optical add-drop multiplexers (ROADMs) into optical networks is driving a need to monitor more than just channel wavelength, power and OSNR.  ROADMs potentially enable faster setting up and testing of new paths in the network, dynamic protection paths, and enhanced fault management.  However, realizing this potential requires a much clearer picture of the impairments inside the network, and their distribution.  

• Monitor performance and margin throughout the network, at the physical layer
• Identify the cause of increasing BER, even with multiple impairments
• Locate the source of the impairment within the network
• Optimise network performance by providing feedback to impairment compensation schemes