Equalization of spectral characterist of optical signanls by acousto-optic filters

Abstract

Use in the main high-speed fiber-optical transmitting systems (FOTS) with spectral compensation of channels of optical amplifiers of a running wave (ARW) leads to distortion of spectral characteristics of a group optical signal. The given distortions after repeated amplification lead to full or partial loss of an alarm stream of those components of a signal which are at edges of a strip of a strengthened spectrum. Equalization the through passage characteristic of each amplifier of a running wave allows to reduce these distortions, however this problem technically represents difficulties. The decision ' this problem probably use of one or several devices of alignment a spectrum in path FOTS which completely would level its through spectral characteristics. Such device has been created on the basis of joint application of the optical amplifier of type ARW and the acousto-optical filter on Superficial acoustic wave (SAW) of type acousto-optical the reconstructed filter (AORF). Application acousto-optical the reconstructed filter allows to equalization through passage spectral characteristics FOTS. As the device for equalization through communicating spectral characteristics the ring scheme (fig.I). The scheme consisted from entrance directed fiber-optical branch - 1, a fiber-optical path - 2, AORF - 3, a fiber-optical path - 4, optical ARW - 5, the day off directed fiber-optical branch - 6, multifrequency electric. The generator - 7, with an opportunity of regulation of target capacity on everyone from frequencies and the adder of electric signals - 8. The device on fig.l works as follows: the spectrally distorted signal from FOTS through 1 and the path 2 gets on optical input AORF. On electric input AORF the complex electric signal representing the sum of fluctuations, different on frequency and amplitude works. Amplitudes of various fluctuations are picked up in such a manner that lengths of waves coming in FOTS a signal which is being at edges of a spectrum, not weakened, and lengths of waves are closer to the central frequency of a spectrum are weakened partially. This process leads to partial alignment of spectral characteristics. Further through a path 4 partially leveled spectrum, gets on an input optical ARW which strengthens an optical signal and through a path 2 again gets on optical input AORF where is exposed to repeated alignment and strengthening. The quantity recircle signal on a ring gets out of a condition of reception of flat spectral characteristics, and also a necessary level of an optical signal on an output of the device.