What is features of OTU in the application of WDM?

what is an OUT？
An Optical Transponder Unit (OTU) board converts client-side services into optical signals carried over ITU-T–compliant WDM wavelengths after performing mapping, multiplexing, convergence, and other operations. OTU boards can be divided into Transponder and Muxponder by function, which are abbreviated as TP and MP respectively.
which is a board in the device in the wavelength division system, and is responsible for the access processing of optical signals.

The optical-electrical-optical conversion method is used to achieve wavelength conversion. 

First, the optical signal received from the client device received by the client optical module is converted into an electrical signal, which is amplified, shaped / clock extracted, and then the electrical signal is modulated onto the laser Output.

Transponder

N into N out: N * low-speed client-side services to N * optical signals carried over ITU-T–compliant WDM wavelengths.

Muxponder

N into 1 out: N * low-speed client-side services to one high-speed optical signal carried over ITU-T–compliant WDM wavelengths.

The features of OTU include:

1. Provide standard and stable light source

Because the DWDM system needs to multiplex multiple wavelengths in a low-loss window and the wavelength interval is small, the center frequency of the DWDM light source needs to work steadily on the nominal center frequency sequence of the ITU-T standard specification.

2. Provide a light source with a larger dispersion value

The increase in the length of the non-electrical relay of the WDM system requires the system to extend the dispersion tolerance distance of the light source and be able to overcome the nonlinear effect of the optical fiber.

3. Use as a regenerator

When the converter is used as a regenerator, it has a data regeneration function. Data regeneration is an optional function of the wavelength converter.