The filter response functions have been designed to be broad and flat over the desired passband in order to support new coherent systems operating in the 60 to 128 Gbaud range.

For the past two decades, AWGs have been a key filtering technology used in dense wavelength division multiplexing (DWDM) systems to add and remove different wavelength channels from transmission fibers. An AWG offers a much lower cost and many more channels compared to a wavelength-selective switch, and is an ideal wavelength multiplexing and demultiplexing technology for high-capacity point-to-point data center interconnect (DCI) systems.

The advent of coherent transmission for telecommunications increases fiber capacity and is useful for DCI applications. However, it imposes a new set of requirements on AWGs that are quite different from those of traditional direct-sensing systems. By using higher transmission rates and higher-order coherent modulation, the bandwidth of each wavelength channel can be increased to 400 Gbps, 600 Gbps, 800 Gbps, or more. However, these channels require more spectral bandwidth, thus reducing the total number of achievable channels when the total available optical spectrum is fixed.

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