Improved frequency response of a semiconductor-optical-amplifier wavelength converter using a fiber Bragg grating

We demonstrated a novel SOA-fiber-grating wavelength converter for RZ data that has a better frequency response than a single SOA wavelength converter at the same optical power level. The SOA-fiber-grating wavelength converter uses a single amplifier and requires no interferometers. The principle of this device is described as follows: Consider an input pump beam at /spl lambda//sub 1/ and a CW probing signal at /spl lambda//sub 2/ coincident in the amplifier. The pump beam partially depletes the gain of the amplifier. This rapidly increases the refractive index of the semiconductor and chirps the CW signal at /spl lambda//sub 1/ towards the red, There is a smaller, blue chirp associated with the slower recovery of the amplifier´s gain. The probing signal´s wavelength, /spl lambda//sub 2/, is adjusted such that the fiber grating passes the red chirped portion of the CW signal and blocks its unchanged spectral components. We use a more compact, fiber grating step filter than previous devices which selects the phase modulated portions of the probing signal more effectively.