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US 6,078,414 AGranted
Optical transmitter system
AssigneeNEC Corporation
InventorTadayuki Iwano
Life of this patent
Estimating the term…
Abstract
An optical transmitter system includes a semiconductor laser, an external modulator, a detector and a frequency-modulation controller. The semiconductor laser transmits an optical signal of a predetermined wavelength onto an optical fiber and a backscattering wave caused by the optical signal is detected by the detector. The frequency-modulation controller controls the semiconductor laser so that the amplitude of a frequency-modulation signal applied to the semiconductor laser is varied depending on a detection signal of the backscattering wave.
Claims17
A circuit comprising:
- a plurality of optical transmitters each comprising:
- (i) a laser light source which produces a light wave of a different wavelength;
- (ii) an optical modulator which modulates the light wave according to input data to produce an optical signal;
- and
- (iii) a frequency-modulation driver which drives the laser light source in predetermined frequency modulation;
- an optical coupler which combines optical signals received from the optical transmitters to produce optical wavelength-division multiplexing (WDM) signals;
- an optical amplifier which amplifies the optical WDM signals for transmission onto an optical fiber;
- a detector which sequentially detects back-propagating waves caused by respective ones of the optical WDM signals from the optical fiber to produce a plurality of corresponding detection signals, the back-propagating waves propagating in a direction opposite to the optical WDM signals;
- and
- a controller which sequentially controls the frequency-modulation drivers of said plurality of optical transmitters to vary a degree of frequency modulation performed by the frequency-modulation drivers depending on respective ones of said detection signals.
7 more elements
A circuit, comprising:
- a plurality of optical transmitters each comprising:
- (i) a laser light source for producing a light wave of a different wavelength,
- (ii) an optical modulator for modulating the light wave according to input data to produce an optical signal, and
- (iii) a frequency-modulation driver for driving the laser light source in predetermined frequency modulation;
- an optical coupler for combining optical signals received from the optical transmitters to produce optical wavelength-division multiplexing (WDM) signals;
- an optical fiber amplifier for amplifying the optical WDM signals to transmit onto an optical fiber;
- a detector for detecting a back-propagating wave caused by each of the optical WDM signals from the optical fiber to produce a detection signal, the back-propagating wave propagating in opposite direction of he optical WDM signals;
- and
- a controller for controlling the frequency-modulation driver an an optical transmitter transmitting the optical signal to vary a degree of frequency modulation depending on the detection signal,
- wherein the detector comprises:
- an optical coupler for receiving back-propagating waves from the optical fiber, the back-propagating waves having different wavelengths in a wavelength range;
- a selector for selecting one of the back-propagating waves in a predetermined sequence;
- and
- a converter for converting a selected back-propagating wave to the detection signal.
11 more elements
An optical transmitter system comprising:
- a plurality of optical transmitters each comprising:
- (i) a semiconductor laser which produces a light wave of a predetermined wavelength, the semiconductor laser being driven by a bias current combined with a control signal for broadening a spectral line width of the light wave;
- and
- (ii) an external modulator which intensity-modulates the light wave according to input data to produce an optical signal which is transmitted onto an optical fiber;
- a detector which sequentially detects back-scattering waves caused by respective ones of the optical WDM signals due to Stimulated Brillouin Scattering (SBS) occurring in the optical fiber to produce detection signals;
- and
- a controller which sequentially controls a magnitude of the control signals corresponding to the optical signal produced from each of said optical transmitters depending on respective ones of the detection signals.
4 more elements
An optical transmitter system, comprising:
- a plurality of optical transmitters each comprising:
- (i) a semiconductor laser for producing a light wave of a predetermined wavelength, the semiconductor laser being driven by a bias current combined with a control signal for broadening a spectral line width of the light wave;
- and
- (ii) an external modulator for intensity-modulating the light wave according to input data to produce an optical signal which is transmitted onto an optical fiber;
- a detector for detecting a back-scattering wave caused by each of the optical WDM signals due to Stimulated Brillouin Scattering (SBS) occurring in the optical fiber to produce a detection signal;
- and
- a controller for controlling a magnitude of the control signal corresponding to the optical signal depending on respective ones of the detection signal,
- wherein the detector comprises:
- an optical coupler for receiving back-scattering waves from the optical fiber, the back-scattering waves having different wavelengths in a wavelength range;
- a selector for selecting one of the back-scattering waves in a predetermined sequence;
- and
- a converter for converting a selected back-scattering wave to the detection signal.
9 more elements
A control method for a plurality of optical transmitters each including a laser light source for producing a light wave of a different wavelength, an optical modulator for modulating the light wave according to input data to produce an optical signal, and a frequency-modulation driver for driving the laser light source in predetermined frequency modulation, the control method comprising the steps of:
- a) combining optical signals received from the optical transmitters to produce optical wavelength-division multiplexing (WDM) signals;
- b) amplifying the optical WDM signals for transmission onto an optical fiber;
- c) sequentially detecting back-propagating waves caused by respective ones of the optical WDM signals from the optical fiber to produce corresponding detection signals, the back-propagating waves propagating in an opposite direction of the optical WDM signals;
- and
- d) sequentially controlling the frequency-modulation drivers of said optical transmitters to vary a degree of frequency modulation performed by the frequency-modulation drivers depending on respective ones of the detection signals.
2 more elements
A control method for a plurality of optical transmitters each comprising a laser light source for producing a light wave of a different wavelength, an optical modulator for modulating the light wave according to input data to produce an optical signal, and a frequency-modulation driver for driving the laser light source in predetermined frequency modulation, the control method comprising the steps of:
- a) combining optical signals received from the optical transmitters to produce optical wavelength-division multiplexing (WDM) signals;
- b) amplifying the optical WDM signals for transmission onto an optical fiber;
- c) detecting a back-propagating wave caused by each of the optical WDM signals from the optical fiber to produce a detection signal, the back-propagating wave propagating in opposite direction of the optical WDM signals;
- and
- d) controlling the frequency-modulation driver of an optical transmitter transmitting the optical signal to vary a degree of frequency modulation depending on the detection signal,
- wherein the step c) comprises the steps of:
- receiving back-propagating waves from the optical fiber, the back-propagating waves having different wavelengths in a wavelength range;
- selecting one of the back-propagating waves in predetermined sequence;
- and converting a selected back-propagating wave to the detection signal.
6 more elements
A feedback loop for suppression of Stimulated Brillouin Scattering (SBS) in an optical transmitter system, comprising:
- a plurality of optical transmitters, each optical transmitter comprising:
- (i) a semiconductor laser for producing a light wave of the predetermined wavelength, the semiconductor laser being driven by a bias current combined with a control signal for broadening a spectral line width of the light wave, and
- (ii) an external modulator for intensity-modulating the light wave according to input data to produce an optical signal which is transmitted onto an optical fiber;
- a detector for selectively detecting back-scattering waves caused by optical signals output from said plurality of optical transmitters due to SBS to produce detection signals, respectively;
- and
- a laser controller for controlling a magnitude of the control signals of said optical transmitters based on respective ones of said detection signals.
3 more elements
Dependencies are inferred from the claim text.