Fiber Optic Tech
1. Working band
The working band of WDM devices, such as 1550 wavelength, distinguishes three bands: S band (short wavelength band 1460~1528nm), C band (conventional band 1530~1565nm), L band (long wavelength band 1565~1625nm).
2. Number of channels and channel spacing
The number of channels refers to the number of channels that can be synthesized or separated by the wavelength division multiplexer/demultiplexer. This number can vary from 4 to 160. The design can be enhanced by adding more channels. The common channel numbers are 4, 8, 16, 32, 40, 48, etc. Channel spacing refers to the difference between the nominal carrier frequencies of two adjacent channels, which can be used to prevent inter-channel interference. According to the suggestion of ITU-T G.692, there are 100GHz (0.8nm), 50GHz (0.4nm) and 25GHz for intervals less than 200GHz (1.6nm), and 100GHz and 50GHz channel intervals are preferred at present.
3. Insertion loss
Insertion loss is the attenuation caused by the insertion of a wavelength division multiplexer (WDM) in an optical transmission system. The attenuation effect of the wavelength division multiplexer itself on the optical signal directly affects the transmission distance of the system. In general, the lower the insertion loss, the less signal attenuation.
Isolation refers to the degree of isolation between signals of each channel. A high isolation value can effectively prevent crosstalk between signals and cause transmission signal distortion.
5. Polarization dependent loss PDL
Polarization-dependent loss PDL is the distance between the maximum and minimum Loss caused by different polarization states at a fixed temperature, wavelength and the same Band, that is, the maximum deviation of insertion loss under all input polarization states.
In addition to the above, there are of course other performance parameters that affect WDM devices, such as operating temperature and bandwidth.