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Fiber Bragg Grating based DCMs
Dispersion compensation utilizing FBGs is based on the introduction of wavelength‐specific time delays through the use of a precisely chirped FBG. By combining an FBG with a standard optical circulator a highly effective Dispersion Compensation Module (DCM) can be realized.
FBG‐DCMs are devised by basically assembling an optical circulator and a chirped FBG. The basic principle is to achieve the compression of a dispersion broadened pulse by letting the “fast” wavelengths of the pulse be reflected further away in the FBG than the “slow” wavelengths that are reflected closer to the circulator. Two main types of FBG based dispersion compensators are commercially available today, multi‐channel (or channelized) and continuous. The channelized version provides channel spacing specific, or grid specific, compensation whereas the continuous type provides, in much the same manner as a DCF, continuous compensation throughout the C‐band, hence providing total channel plan independency.
One additional benefit of having a continuous FBG is that no athermal package or temperature control is required for the component, as there is no need to prevent the DCM operating bandwidth to glide out of the ITU channel.