The DCM-20 from Fiberdyne Labs is a Dispersion Compensation Module with Compensated Fiber Length(Distance) 20 km, Dispersion Compensation Level -340±10 ps/nm, Insertion Loss 2.9 to 3.5 dB, Wavelength Range 1525 to 1565 nm, Polarization Dependent Loss <0.1 dB. More details for DCM-20 can be seen below.