Wavelength Conversion
Wavelength conversion is done by a transponder and can convert a wavelength from 850nm or 1310nm to 1550nm. A transponder can also convert from 850nm or 1310nm to a specific CWDM or DWDM wavelength. Conversion from 850nm would typically be done at a client to network interface whereas conversion from 1310nm would be done at either a client to network interface or a network to network interface.
The Optelian RGN series of regenerators can perform wavelength conversion from 850nm or 1310nm to 1550nm or to specific CWDM or DWDM wavelengths.