Clock regeneration circuit and optical signal receiver using the same

An optical signal receiver, comprising:

• a light receiving element for converting a received light signal into a reception electric signal;
• a PLL circuit which includes a voltage control oscillator, for synchronizing an oscillation frequency signal of the voltage control oscillator with a phase of a reception electric signal;
• a clock extraction circuit which includes a band passing filter having a passing band width which concurrently extracts a basic waves component of the oscillation frequency signal of the voltage control oscillator and a harmonic component of a dividing signal of the oscillation frequency signal, for extracting a clock component of the reception signal;
• a frequency detector for detecting a difference in frequencies between an output of the clock extraction circuit and an oscillation frequency of the voltage control oscillator;
• a loop filter for controlling the oscillation frequency of the voltage control oscillator of the PLL circuit by a detection output of the frequency detector;
• a discriminator for discriminating a level of the reception electric signal at a frequency timing of the output of the PLL circuit to output discrimination data;
• a bit rate detection circuit for detecting a bit rate of the reception signal;
• and
• a frequency selection circuit for outputting an oscillation frequency of the voltage control oscillator of the PLL circuit or a frequency signal obtained by dividing the oscillation frequency in response to the bit rate detected by the bit rate detection circuit, as a regeneration clock signal.