Control method and apparatus for stabilizing optical wavelength

A control apparatus for stabilizing the wavelength of light output from a laser, comprising:

• parameter deviation detecting means for detecting a first control deviation of one parameter responsible for causing variations of optical wavelength output from the laser from a predetermined target value,
• optical wavelength deviation detecting means for detecting a second control deviation of optical wavelength output from the laser from a predetermined target value,
• selecting means for selecting either of said first and second control deviations, and
• manipulating means for manipulating one of said parameters so that said selected control deviation is reduced.

A control apparatus for stabilizing the wavelength of light output from a laser module including a laser element, a temperature sensor and a cooling/heating element, comprising:

• first control means for stabilizing said optical wavelength,
• second control means for stabilizing said optical wavelength, and
• selecting means for selecting either of said first and second control means according to external conditions, and performing stabilizing control of the optical wavelength of said laser element according to an output signal from the selected control means, wherein:
• said first control means comprises a temperature monitor for monitoring the temperature of the laser detected by said temperature sensor, a first comparator for detecting a difference between the output value of the temperature monitor and a laser temperature control target value, and first current control means for controlling the current flowing in said cooling/heating element according to an output signal from said first comparator, and
• said second control means comprises an optical coupler for splitting the output light from the laser module, an optical wavelength monitor for monitoring the wavelength of the split output light, a second comparator for detecting a difference between the monitored optical output wavelength value and a wavelength control target value, and second current control means for controlling the current flowing in said cooling/heating element according to an output signal from said second comparator.

An optical wavelength division multiplexer for transmitting a plurality of light signals having different wavelengths to each other, comprising:

• a plurality of laser diodes installed on a common heat sink,
• a temperature controller for controlling the temperature of said heat sink to a predetermined temperature,
• an optical sensor for detecting oscillation wavelengths of said laser diodes,
• a driving current source for driving said laser diodes, and
• a current controller for controlling the currents with which said driving current source drives said laser diodes such that the detected oscillation wavelengths of said laser diodes approach predetermined target wavelengths for each laser diode,
• wherein said current controller controls the driving current of one of said plural laser diodes so that it approaches a predetermined target current when the output light from said laser diode has shut down, and a predetermined time from starting optical output has not elapsed.

An optical wavelength division multiplexer for transmitting a plurality of light signals having different wavelengths to each other, comprising:

• a plurality of laser diodes,
• a driving current source for driving said laser diodes,
• an optical sensor for detecting oscillation wavelengths of said laser diodes,
• a temperature sensor for detecting temperatures of said laser diodes, and
• a temperature controller for controlling the temperature of each of said laser diodes so that a detected oscillation wavelength approaches a predetermined target wavelength for the laser diode when the oscillation wavelength of the laser diode is stably detected, and for controlling the temperature of each of said laser diode to a predetermined temperature for each laser diode when the oscillation wavelength of said laser diode is not stably detected.

A control method for stabilizing the wavelength of light output by a laser, comprising:

• detecting a first control deviation of one parameter responsible for causing variations of optical wavelength output from the laser from a predetermined target value,
• detecting a second control deviation of optical wavelength output from the laser from a predetermined target value,
• selecting either of said first and second control deviations, and
• manipulating one of said parameters so that said selected control deviation is reduced.