Optical receiving apparatus and method

Abstract

An optical receiving apparatus according to the present invention comprises an optical receiver for receiving a signal light input from an optical transmission line, a discriminator for discriminating an output signal of the optical receiver, an evaluator for evaluating transmission characteristics of the optical transmission line according to the received signal of the optical receiver, and a threshold controller for controlling the discrimination threshold of the discriminator according to the evaluated result of the evaluator.

1 . An optical receiving apparatus, comprising: 
 an optical receiver to receive a signal light input from an optical transmission line;    a discriminator to discriminate an output signal of the optical receiver;    an evaluator to evaluate transmission characteristics of the optical transmission line according to the received signal of the optical receiver; and    a threshold controller to control a discrimination threshold of the discriminator according to the evaluated transmission characteristics;    wherein the evaluator comprises a plurality of measuring discriminators to discriminate the signal received at the optical receiver according to a plurality of fixed thresholds being different from each other, an error measurer to measure information about an error number contained in an output of the respective measuring discriminators, and a standard deviation calculator to calculate at least one of standard deviations on mark and space sides from the measured information of the error measurer.    
     
     
         2 . The optical receiving apparatus of  claim 1  wherein the threshold controller determines an optimum discrimination threshold of the discriminator according to variations of bit error rates on mark and space sides obtained from the measured information of the error measurer.  
     
     
         3 . An optical receiving apparatus, comprising: 
 an optical receiver to receive a signal light input from an optical transmission line;    a discriminator to discriminate an output signal of the optical receiver;    an evaluator to evaluate transmission characteristics of the optical transmission line according to the received signal of the optical receiver; and    a threshold controller to control a discrimination threshold of the discriminator according to the evaluated transmission characteristics;    wherein the evaluator comprises a clock extractor to extract a clock from the received signal, and the threshold controller determines an optimum discrimination threshold of the discriminator according to an amplitude of an output from the clock extractor.    
     
     
         4 . An optical receiving apparatus, comprising: 
 an optical receiver to receive a signal light input from an optical transmission line;    a discriminator to discriminate an output signal of the optical receiver;    an evaluator to evaluate transmission characteristics of the optical transmission line according to the received signal of the optical receiver; and    a threshold controller to control a discrimination threshold of the discriminator according to the evaluated transmission characteristics;    wherein the optical receiver comprises a photodetector to convert the input signal light from the optical transmission line into an electric signal, and an electric brancher to apply an output of the photodetector to the discriminator and evaluator.    
     
     
         5 . An optical receiving apparatus, comprising: 
 an optical receiver to receive a signal light input from an optical transmission line;    a discriminator to discriminate an output signal of the optical receiver;    an evaluator to evaluate transmission characteristics of the optical transmission line according to the received signal of the optical receiver; and    a threshold controller to control a discrimination threshold of the discriminator according to the evaluated transmission characteristics;    wherein the optical receiver comprises an optical brancher to branch the input signal light from the optical transmission line into a plurality of output lights, and a plurality of photodetectors to convert the respective output lights from the optical brancher into electric signals.    
     
     
         6 . An optical receiving apparatus, comprising: 
 an optical receiver to receive a signal light input from an optical transmission line;    a discriminator to discriminate an output signal of the optical receiver;    an evaluator to evaluate transmission characteristics of the optical transmission line according to the received signal of the optical receiver; and    a threshold controller to control a discrimination threshold of the discriminator according to the evaluated transmission characteristics;    wherein the evaluator comprises an amplitude evaluator to evaluate an amplitude of the output signal from the optical receiver.    
     
     
         7 . The optical receiving apparatus of  claim 6  wherein the amplitude evaluator comprises a saturable absorber.  
     
     
         8 . A method for optical reception, comprising: 
 receiving an input signal light from an optical transmission line to output a received signal;    discriminating the received signal;    evaluating transmission characteristics of the optical transmission line according to the received signal; and    controlling a discrimination threshold for the discrimination of the received signal according to the evaluated transmission characteristics;    wherein the evaluation of the transmission characteristics comprises discriminating the received signal according to a plurality of fixed thresholds being different from each other, measuring information about an error number resulting therefrom, and calculating at least one of standard deviations on mark and space sides from the measured information.    
     
     
         9 . The optical receiving method of  claim 8  wherein the evaluation of the controlling of the discrimination threshold comprises determining an optimum discrimination threshold according to variations of bit error rates on mark and space sides obtained from the measured information.  
     
     
         10 . A method for optical reception, comprising: 
 receiving an input signal light from an optical transmission line to output a received signal;    discriminating the received signal;    evaluating transmission characteristics of the optical transmission line according to the received signal; and    controlling a discrimination threshold for the discrimination of the received signal according to the evaluated transmission characteristics;    wherein the evaluation of the transmission characteristics comprises extracting a clock from the received signal, and the controlling of the discrimination threshold comprises determining an optimum discrimination threshold according to an amplitude of the extracted clock.