Optical pulse generation system for generating optical pulses having high duty ratio

• US 6,483,624 B1
• Filed: 12/06/1999
• Issued: 11/19/2002
• Est. Priority Date: 12/24/1998
• Status: Expired due to Fees

• Current Assignee: Anritsu Corporation
• Original Assignee: Anritsu Corporation
• Inventors: Otani, Akihito, Otsubo, Toshinobu
• Primary Examiner(s): Chan, Jason
• Assistant Examiner(s): Kim, David S.
• Application Number:
  US09/455,562
• Time in Patent Office: 1,079 Days
• Field of Search: 359/248, 359/125, 359/183, 359/264, 359/181, 359/158, 359/184, 359/187, 359/154, 375/238, 375/259, 375/295, 385/27
• US Class Current: 398/201
• CPC Class Codes: G02F 1/0121 Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
• CPC Class Codes: G02F 1/015 based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction G02F1/03 takes precedence

Abstract

An optical pulse generator includes a single-wavelength light source, an electroabsorption optical modulator, a sine-wave voltage generator, a nonlinear circuit, and a DC voltage source. The single-wavelength light source outputs continuous, single-wavelength light. The electroabsorption optical modulator receives the single-wavelength light, modulates the single-wavelength light according to a pulse modulation signal, and outputs the modulated light as optical pulses. The sine-wave voltage generator generates an electrical signal having a sine waveform. The nonlinear circuit extracts only a waveform equal to or higher than a predetermined DC voltage from the sine waveform electrical signal. The DC voltage source adds a negative DC voltage to the electrical signal, from which only the waveform equal to or higher than the predetermined DC voltage is extracted by the nonlinear circuit, and applies the sum signal to the electroabsorption optical modulator as the pulse modulation signal.

Claims

1. An optical pulse generation method in which a pulse modulation signal is applied to an electroabsorption optical modulator while continuous, single-wavelength light is launched into the electroabsorption optical modulator so as to modulate the incoming single-wavelength light by the pulse modulation signal and to output the modulated light as optical pulses, comprising the steps of:

generating an electrical signal having a sine waveform;

extracting only a waveform not less than a predetermined DC voltage from the sine waveform of the electrical signal; and

adding a negative DC voltage to the extracted waveform, and applying the sum signal to the electroabsorption optical modulator as the pulse modulation signal.

2. An optical pulse generation device comprising:

a single-wavelength light source for outputting continuous, single-wavelength light;

an electroabsorption optical modulator for receiving the single-wavelength light output from said single-wavelength light source, modulating the incoming single-wavelength light according to an externally applied pulse modulation signal, and outputting the modulated light as optical pulses;

a sine-wave voltage generator for generating an electrical signal having a sine waveform;

a nonlinear circuit for extracting only a waveform not less than a predetermined DC voltage from the sine waveform of the electrical signal generated by said sine-wave voltage generator; and

a DC voltage source for adding a negative DC voltage to the extracted waveform by said nonlinear circuit, and applying the sum signal to said electroabsorption optical modulator as the pulse modulation signal.

3. A device according to claim 2, wherein said nonlinear circuit comprises:

a half-wave rectification circuit for outputting a half-wave rectified signal of the electrical signal having the sine waveform, which is output from said sine-wave voltage generator; and

a voltage amplifier for voltage-amplifying the half-wave rectified signal output from said half-wave rectification circuit.

4. A device according to claim 2, wherein said nonlinear circuit comprises a voltage amplifier, an operation point of which can be shifted, and voltage-amplifies the electrical signal having the sine waveform output from said sine-wave voltage generator while the operation point is shifted in a negative direction.

5. An optical pulse generation device comprising:

a single-wavelength light source for outputting continuous, single-wavelength light;

a first electroabsorption optical modulator for receiving the single-wavelength light output from said single-wavelength light source, modulating the incoming single-wavelength light according to an externally applied pulse modulation signal, and outputting the modulated light as optical pulses;

a first modulation signal generation circuit comprising

a) a sine-wave voltage generator for generating an electrical signal having a sine waveform,

b) a nonlinear circuit for extracting only a waveform not less than a predetermined DC voltage from the sine waveform of the electrical signal generated by said sine-wave voltage generator, and

c) a DC voltage source for adding a negative DC voltage to the extracted waveform by said nonlinear circuit, and applying the sum signal to said first electroabsorption optical modulator as the pulse modulation signal;

a second electroabsorption optical modulator for receiving the optical pulses output from said first electroabsorption optical modulator, modulating the incoming optical pulses according to an externally applied pulse modulation signal, and outputting the modulated optical pulses as final optical pulses; and

a second modulation signal generation circuit comprising

a) a DC voltage source for outputting a negative DC voltage,

b) a rectangular wave signal generation circuit for outputting a rectangular wave signal, and

c) a sync adjustment circuit,

said second modulation signal generation circuit synchronously adjusting the rectangular wave signal output from said rectangular wave signal generation circuit by said sync adjustment circuit to make individual rectangular waves of the rectangular wave signals include optical pulses once every predetermined number of pulses, adding the negative DC voltage output from said DC voltage source to the adjusted rectangular wave signal, and applying the sum signal to said second electroabsorption optical modulator as the pulse modulation signal.

6. An optical pulse generation device comprising:

a single-wavelength light source for outputting continuous, single-wavelength light;

an electroabsorption optical modulator for receiving the single-wavelength light output from said single-wavelength light source, modulating the incoming single-wavelength light according to an externally applied pulse modulation signal, and outputting the modulated light as optical pulses;

a modulation signal generation circuit comprising

a) a sine-wave voltage generator for generating an electrical signal having a sine waveform,

b) a nonlinear circuit for extracting only a waveform not less than a predetermined DC voltage from the sine waveform of the electrical signal generated by said sine-wave voltage generator, and

c) a DC voltage source for adding a negative DC voltage to the extracted waveform by said nonlinear circuit, and applying the sum signal to said electroabsorption optical modulator as the pulse modulation signal; and

a dispersion decreasing fiber for receiving the optical pulses output from said electroabsorption optical modulator at one end, and outputting the incoming optical pulses as final optical pulses from the other end.

7. An optical sampling pulse generation device for outputting optical sampling pulses used to sample light to be measured, which enters a light sampling unit in a light sampling waveform measurement apparatus, comprising:

a single-wavelength light source for outputting continuous, single-wavelength light;

a first electroabsorption optical modulator for receiving the single-wavelength light output from said single-wavelength light source, modulating the incoming single-wavelength light according to an externally applied pulse modulation signal, and outputting the modulated light as optical pulses;

a first modulation signal generation circuit comprising

a) a nonlinear circuit for extracting only a waveform not less than a predetermined DC voltage from an electrical signal having a sine waveform, and

b) a DC voltage source for adding a negative DC voltage to the extracted waveform by said nonlinear circuit, and applying the sum signal to said first electroabsorption optical modulator as the pulse modulation signal;

a second electroabsorption optical modulator for receiving the optical pulses output from said first electroabsorption optical modulator, modulating the incoming optical pulses according to an externally applied pulse modulation signal, and outputting the modulated optical pulses as final optical pulses; and

a second modulation signal generation circuit comprising

a) a DC voltage source for outputting a negative DC voltage,

b) a rectangular wave signal generation circuit for outputting a rectangular wave signal, and

c) a sync adjustment circuit,

said second modulation signal generation circuit synchronously adjusting the rectangular wave signal output from said rectangular wave signal generation circuit by said sync adjustment circuit to make individual rectangular waves of the rectangular wave signals include optical pulses once every predetermined number of pulses, adding the negative DC voltage output from said DC voltage source to the adjusted rectangular wave signal, and applying the sum signal to said second electroabsorption optical modulator as the pulse modulation signal;

a dispersion decreasing fiber for receiving the optical pulses output from said second electroabsorption optical modulator at one end, and outputting the incoming optical pulses as final optical pulses from the other end;

a timing clock generation circuit for supplying a first sampling clock signal which is delayed a predetermined time from a clock signal based on a repetition period of the light to be measured to said nonlinear circuit of said first modulation signal generation circuit as the electrical signal having the sine waveform; and

a frequency divider for supplying a second sampling clock signal which is obtained by frequency-dividing the first sampling clock signal from said timing clock generation circuit at a predetermined ratio to said sync adjustment circuit of said second modulation signal generation circuit.