Title:
AUTOMATIC CONTROL CIRCUIT FOR OPTICAL MODULATOR BIAS
Document Type and Number:
Japanese Patent JPH04294318
Kind Code:
A
Abstract:
PURPOSE:To offer the circuit which automatically adjusts the bias so that the operation point of a Mach-Zehnder optical modulator is held at the best point at all times. CONSTITUTION:The respective mean powers of the optical modulator 41 which generates complementary light outputs are monitored by photodetectors 7 and 42 and a subtracting circuit 43 generates a monitor voltage which is proportional to their difference. The monitor voltage is compared by an error detector 13 with a reference voltage and a bias voltage corresponding to the difference is impressed to the optical modulator to hold the bias at the best value. A mark rate detecting circuit 61 is used and then the reference voltage varies with the mark rate of a modulated signal. This phase of the operation point is detected by comparators 73a and 73b and a function for hopping a bias voltage into a controllable area is provided. Consequently, the bias is automatically adjusted to the best value at all times without being affected by level variation of a light source, mark rate variation of the modulated signal, and the phase of the operation point when the power source is turned on.
Inventors:
MIZUOCHI TAKASHI
KITAYAMA TADAYOSHI
KITAYAMA TADAYOSHI
Application Number:
JP5928191A
Publication Date:
October 19, 1992
Filing Date:
March 25, 1991
Export Citation:
Assignee:
MITSUBISHI ELECTRIC CORP
International Classes:
G02F1/035; G02F1/01; G02F1/03; (IPC1-7): G02F1/035; G02F1/05
Attorney, Agent or Firm:
Mamoru Takada (1 person outside)