Optical receiving apparatus and method

Abstract

It is aimed at providing an optical receiving apparatus and an optical receiving method, which can assuredly receive and process signal lights having different transmission rates, by a simple and single device. To this end, the signal light received by the present optical receiving apparatus is converted into an electric signal by a light receiving element and thereafter sent to an equalizing amplifier whereby the signal is amplified. The transmission rate of this received signal is detected by a transmission rate detecting part, and a band of the equalizing amplifier is optimally controlled by an equalizing band controlling part, corresponding to the detected transmission rate. In case of adopting a PLL (phase-locked loop) circuit as a clock generating circuit, there is also controlled a band of a loop filter corresponding to the transmission rate detected by the transmission rate detecting part. Thus, there can be obtained an excellent reception characteristics, even when receiving signal lights having different transmission rates.

What is claimed is:  
     
         1 . An optical receiving method comprising: 
 receiving each of signal lights having different transmission rates and converting said received signal light into an electric signal;    detecting a transmission rate of said received signal light; and    equalizing-amplification-controlling a variable band of equalizing amplifying means which linearly amplifies said converted electric signal, wherein 
 said equalizing amplification-controlling comprises: 
 controlling said band of said equalizing-amplifying means to be a maximum value of said band, when the transmission rate of said received signal light has been changed; and  
 controlling, on and after the transmission rate after shifting has been detected, said band of said equalizing-amplifying means to be an optimal value corresponding to said detected transmission rate.  
 
   
     
     
         2 . An apparatus comprising: 
 a light receiving device receiving a plurality of signal lights having different transmission rates and converting the respective received signal light into an electrical signal;    an equalizing-amplifying device having a band and linearly amplifying the electrical signal;    a first controlling device controlling said band to be a maximum value of said band when it is detected that a transmission rate of the respective signal light received by said light receiving device has changed; and    a second controlling device controlling said band to be an optimal value which corresponds to the detected transmission rate.