Method of driving semiconductor laser with wide modulation band, optical communication method, semiconductor laser device, node, and optical communication system
AssigneeCanon Kabushiki Kaisha
InventorsToshihiko Ouchi, Masao Majima
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Abstract
This invention discloses the following. Two modulation currents are injected into different electrodes of a semiconductor laser having a plurality of electrodes. The relationship between the phases of the two modulation currents is so adjusted that an output waveform is not distorted especially when a modulation frequency is low. Polarization modulation is applied as the modulation form.
Claims83
A semiconductor laser driving method of driving a semiconductor laser having not less than two electrodes by switching two polarization modes with different planes of polarization, comprising the steps of:
- injecting a main modulation current into one of said electrodes;
- and
- injecting a sub-modulation current whose phase is adjusted with respect to the main modulation current into at least one of said electrodes except for the electrode into which the main modulation current is injected.
An optical communication method in an optical communication system which transmits information in the form of an optical signal between nodes, comprising the steps of:
- switching two polarization modes of an output from a semiconductor laser having a plurality of electrodes in accordance with information to be transmitted in a node for transmitting information;
- outputting light having one of the two polarization modes to an optical transmission line;
- and
- receiving the optical signal on said optical transmission line in a node for receiving information,
- wherein the step of switching the two polarization modes comprises the substeps of:
- injecting a main modulation current corresponding to the information to be transmitted into one of said electrodes;
- and
- injecting a sub-modulation current whose phase is adjusted with respect to the main modulation current into at least one of said electrodes except for the electrode into which the main modulation current is injected.
A semiconductor laser device for outputting two polarization modes with different planes of polarization by switching the two polarization modes, comprising:
- a semiconductor laser having not less than two electrodes;
- means for injecting a main modulation current into one of said electrodes of said semiconductor laser;
- and
- means for injecting a sub-modulation current whose phase is adjusted with respect to the main modulation current into at least one of said electrodes except for the electrode into which the main modulation current is injected.
A semiconductor laser device for outputting two polarization modes with different planes of polarization by switching the polarization modes, comprising:
- a semiconductor laser having not less than two electrodes;
- a modulation power supply;
- first injecting means for passing an output from said modulation power supply through a first amplifier and injecting the output as a first modulation current into one of said electrodes of said semiconductor laser;
- and
- second injecting means for passing the output from said modulation power supply through a second amplifier and injecting the output as a second modulation current into at least one of said electrodes except for the electrode into which said first injecting means injects the first modulation current,
- wherein a cutoff frequency of said second amplifier is a predetermined frequency, and the second modulation current is not injected if a frequency of the output from said modulation power supply exceeds the predetermined frequency.
A semiconductor laser device for outputting two polarization modes with different planes of polarization by switching the polarization modes, comprising:
- a semiconductor laser having not less than two electrodes;
- a modulation power supply;
- first injecting means for passing an output from said modulation power supply through a first voltage-current converter, DC-coupling an output from said first voltage-current converter and a first DC current, and injecting the resultant current as a first modulation current into one of said electrodes of said semiconductor laser;
- and
- second injecting means for passing the output from said modulation power supply through a second voltage-current converter, DC-coupling an output from said second voltage-current converter and a second DC current, and injecting the resultant current as a second modulation current into at least one of said electrodes except for the electrode into which said first injecting means injects the first modulation current,
- wherein said second injecting means has a low-pass filter with a predetermined cutoff frequency for filtering the output from said second voltage-current converter, and the second modulation current is not injected if a frequency of the output from said modulation power supply exceeds the predetermined frequency.
A node used in an optical communication system for transmitting information in the form of an optical signal between nodes, comprising:
- a semiconductor laser device for outputting two polarization modes with different planes of polarization by switching the polarization modes in accordance with information to be transmitted;
- and
- polarization mode selecting means for selectively outputting one of the two polarization modes of the output from said semiconductor laser device;
- wherein said semiconductor laser device comprises:
- a semiconductor laser having not less than two electrodes;
- means for injecting a main modulation current corresponding to the information to be transmitted into one of said electrodes of said semiconductor laser;
- and
- means for injecting a sub-modulation current whose phase is adjusted with respect to the main modulation current into at least one of said electrodes except for the electrode into which the main modulation current is injected.
An optical communication system for transmitting information in the form of an optical signal between nodes, comprising:
- a node for transmitting information, comprising:
- a semiconductor laser device for outputting two polarization modes with different planes of polarization by switching the polarization modes in accordance with information to be transmitted;
- and
- polarization mode selecting means for selectively outputting one of the two polarization modes of the output from said semiconductor laser device,
- wherein said semiconductor laser device comprises:
- a semiconductor laser having not less than two electrodes;
- means for injecting a main modulation current corresponding to the information to be transmitted into one of said electrodes of said semiconductor laser;
- and
- means for injecting a sub-modulation current whose phase is adjusted with respect to the main modulation current into at least one of said electrodes except for the electrode into which the main modulation current is injected;
- and
- a node for receiving information comprising:
- means for demodulating an intensity of an optical signal transmitted from said node for transmitting information.
A semiconductor laser device for outputting a light modulated between two polarization modes with different planes of polarization, comprising a semiconductor laser having a first electrode into which a main modulation current is injected and a second electrode into which a sub-modulation current, whose phase is adjusted with respect to the main modulation current, is injected.
A semiconductor laser device for outputting a light modulated between two polarization modes with different planes of polarization, comprising a semiconductor laser having first and second electrodes and a current injector which injects a main modulation current into said first electrode and which injects a sub-modulation current, whose phase is adjusted with respect to the main modulation current, into said second electrode.
Dependencies are inferred from the claim text.