JPH10123578A - Stabilized white pulse light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate white pulse light having an ultra-wide band and high stability by beforehand measuring a relation between a spectrum of white pulse light and a light intensity of excitation pulse light and controlling the light intensity of the excirotion pulse so that the spectrum width of the white pulse light becomes maximum. SOLUTION: The excitation pulse light outgoing from a pulse light course 3 having a light intensity control function is inputted to a waveguide type light nonlinear medium 2. A light intensity control means 4 stabilizes the light intensity of the excitation pulse light to a prescribed value through the light intensity control function of the pulse light source 3. The prescribed value of the light scribed is the value that the relation between the spectrum of the white pulse light generated in the waveguide type light nonlinear medium 2 and the light intensity of the excitation pulse light is measured beforehand, and the spectrum width of the white pulse light obtained from the measured result is made maximum. The light intensity of the excitation pulse light is controlled so that e.g. the temp,. of the pulse light source 3 becomes a prescribed fixed value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white pulse light source that emits excitation pulse light into a waveguide type optical nonlinear medium to generate a broad band white pulse light. In particular, the present invention relates to a stabilized white pulse light source that generates white pulse light having a stable spectral width.

[0002]

2. Description of the Related Art FIG. 10 shows a configuration of a conventional white pulse light source. In the figure, a white pulse light source includes a pulse light source 1 that generates excitation pulse light having a time width of picoseconds to femtoseconds, and an excitation pulse light that is incident and propagates to induce a third-order nonlinear optical effect to generate a white pulse. A waveguide type optical nonlinear medium 2 for generating light.

The pulse light source 1 includes a mode-locked laser (ring type, Fabry-Perot type), a gain switch laser, a CW light source, a pulse light source having a light intensity modulator after the pulse light source, and a phase-modulated CW light. A pulse light source using PM-AM conversion when propagating through a dispersive medium, a white pulse light source with a wavelength filter attached, and the like are used. Further, an optical amplifier or a pulse width compressor may be added to them. As the waveguide type optical nonlinear medium 2, a single mode optical fiber, a polarization maintaining single mode optical fiber, a semiconductor laser waveguide, a planar optical waveguide, a rare earth doped optical waveguide, and others are used.

FIG. 11 shows spectra of white pulse light and excitation pulse light generated by a conventional white pulse light source. The example shown here uses a single-mode optical fiber as the waveguide type optical nonlinear medium 2. The white pulsed light has a spectrum having continuous and flat light intensity over the generated wavelength range. However, since the generation of such white pulse light is caused by the third-order nonlinear optical effect, the spectrum width depends on the peak intensity of the excitation pulse light.

FIG. 12 shows the relationship between the peak intensity of the excitation pulse light and the spectrum width of the white pulse light. Note that this is a case where a single mode optical fiber is used as the waveguide type optical nonlinear medium. As shown here, the peak intensity of the excitation pulse light has a region for obtaining an efficient spectrum width, and the spectrum width becomes smaller even if it is smaller or larger. Therefore, in order to obtain the maximum spectrum width with high stability, it is necessary to stabilize the value of the peak intensity of the excitation pulse light within a predetermined range.

[0006]

However, as shown in FIG. 10, the conventional white pulse light source has no means for stabilizing the peak intensity of the excitation pulse light. The temporal variation of the spectrum width of the white pulse light due to the variation was unavoidable. Such a white pulse light source cannot be used as it is as a light source for an optical communication system or an optical measurement system.

An object of the present invention is to provide a stabilized white pulse light source capable of generating white pulse light having high stability in an ultra-wide band.

[0008]

According to a first aspect of the present invention, there is provided a stabilized white pulse light source, wherein a relationship between a spectrum of a white pulse light generated in a waveguide type optical nonlinear medium and a light intensity of an excitation pulse light is measured in advance. Means is provided for controlling the light intensity of the excitation pulse light so that the light spectrum width is maximized. In this configuration, by stabilizing the light intensity of the excitation pulse light incident on the waveguide type optical nonlinear medium to a value at which the spectral width of the white pulse light is maximized, the white pulse light having high stability in an ultra-wide band is obtained. Is to be generated.

A stabilized white pulse light source according to a second aspect of the present invention includes means for monitoring the spectrum of the white pulse light generated in the waveguide type optical nonlinear medium, and means for controlling the excitation pulse light so as to maximize the spectrum width of the white pulse light. Means for controlling light intensity. In this configuration, by monitoring the white pulse light generated in the waveguide type optical nonlinear medium and controlling the light intensity of the excitation pulse light so as to maximize the spectrum width, the white light having high stability in an ultra-wide band is obtained. A pulse light is generated.

Further, there may be provided means for compensating the chirp of the output white pulse light (claim 3) or means for equalizing the wavelength dependence of the spectrum (claim 4). This makes it possible to generate white pulsed light having a small chirp and a flat spectrum over a wide band.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

(First embodiment of the stabilized white pulse light source of claim 1)
FIG. 1 shows a first embodiment of the stabilized white pulse light source according to claim 1. In FIG. 1, an excitation pulse light output from a pulse light source 3 having a light intensity control function is input to a waveguide type optical nonlinear medium 2. The light intensity controller 4 stabilizes the light intensity of the excitation pulse light to a predetermined value via the light intensity control function of the pulse light source 3. Here, the predetermined value of the light intensity is
This is a value that measures in advance the relationship between the spectrum of the white pulse light generated in the waveguide type optical nonlinear medium 2 and the light intensity of the excitation pulse light, and maximizes the spectrum width of the white pulse light obtained from the measurement result. The same applies to the second embodiment and the third embodiment described below.

The light intensity of the excitation pulse light is controlled, for example, so that the temperature of the pulse light source 3 is constant at a predetermined value or the excitation state of the laser medium of the pulse light source 3 is constant at a predetermined value. You can take a way. The latter method of controlling the excitation state of the laser medium is a method of controlling the injection current when using a current injection laser medium such as a semiconductor laser, and a method of controlling the excitation light intensity when using an optically pumped laser medium such as a rare earth doped fiber. Can be realized by:
With such a configuration, the light intensity of the excitation pulse light incident on the waveguide-type optical nonlinear medium 2 is controlled to a value that maximizes the spectral width of the white pulse light, and the optical bandwidth from the waveguide-type optical nonlinear medium 2 is increased. Thus, white pulse light having high stability can be generated.

(Second aspect of the stabilized white pulse light source of claim 1)
FIG. 2 shows a stabilized white light pulse light source according to a second embodiment of the present invention. In the figure, the excitation pulse light output from the pulse light source 3 having the light intensity control function is:
The light is input to the waveguide type optical nonlinear medium 2 and the light intensity detecting means 7 via the optical coupler 6. Light intensity detection means 7
The light intensity of the excitation pulse light detected in (1) is fed back to the light intensity control means 5 as control information. The light intensity control means 5 controls the pulse light source 3 so that the light intensity of the excitation pulse light is stabilized at a predetermined value.

The structure for controlling the light intensity of the excitation pulse light of the pulse light source 3 by the light intensity control means 5 is the same as that by the light intensity control means 4 in the first embodiment. With such a configuration, the light intensity of the excitation pulse light incident on the waveguide-type optical nonlinear medium 2 is controlled to a value that maximizes the spectral width of the white pulse light, and the optical bandwidth from the waveguide-type optical nonlinear medium 2 is increased. Thus, white pulse light having high stability can be generated.

(Third aspect of the stabilized white pulse light source of claim 1)
FIG. 3 shows a stabilized white pulse light source according to a third embodiment of the present invention. In the figure, the excitation pulse light output from the pulse light source 1 similar to the conventional configuration is input to the waveguide type optical nonlinear medium 2 via the optical coupler 6 and the light intensity changing means 8. The excitation pulse light branched by the optical coupler 6 is incident on the light intensity detecting means 7, and the detected light intensity is input to the light intensity varying means 8 as control information. The light intensity varying means 8 controls the light intensity of the excitation pulse light to be a predetermined value.

As the light intensity varying means 8, a variable optical amplifier or a variable optical attenuator is used. Although FIG. 3A shows a feed-forward control configuration, a configuration in which the output light of the light intensity varying means 8 is monitored and feedback-controlled as shown in FIG. With such a configuration,
The light intensity of the excitation pulse light incident on the waveguide-type optical nonlinear medium 2 is controlled to a value that maximizes the spectral width of the white pulse light, and has high stability in an ultra-wide band from the waveguide-type optical nonlinear medium 2. White pulse light can be generated.

(First of the stabilized white pulse light source of claim 2)
Embodiment 1 FIG. 4 shows a first embodiment of a stabilized white pulse light source according to claim 2 of the present invention. In the figure, the excitation pulse light output from the pulse light source 3 having the light intensity control function is:
The light is input to the waveguide type optical nonlinear medium 2. The white pulse light output from the waveguide type optical nonlinear medium 2 is split by the optical coupler 9 and input to the optical spectrum detection means 10, and information indicating the detected spectrum width is fed back to the light intensity control means 5. . The light intensity control means 5 controls the light intensity of the excitation pulse light output from the pulse light source 3 so that the spectrum width of the white pulse light is maximized. The configuration in which the light intensity control means 5 controls the light intensity of the excitation pulse light of the pulse light source 3 is the same as in the embodiment shown in FIG.

The light spectrum detecting means 10 uses a spectral means such as an optical spectrum analyzer. Alternatively, the light intensity of each wavelength component corresponding to the spectrum width of the white pulse light may be detected using a wavelength filter and a light intensity detection unit, and the detected light intensity may be fed back to the light intensity control unit 5.
The same applies to the configuration of the second embodiment described below.
With such a configuration, the light intensity of the excitation pulse light incident on the waveguide-type optical nonlinear medium 2 is controlled to a value that maximizes the spectral width of the white pulse light, and the optical bandwidth from the waveguide-type optical nonlinear medium 2 is increased. Thus, white pulse light having high stability can be generated.

(Second aspect of the stabilized white pulse light source of claim 2)
Embodiment 2 FIG. 5 shows a second embodiment of the stabilized white pulse light source according to claim 2 of the present invention. In the figure, the excitation pulse light output from the pulse light source 1 similar to the conventional configuration is input to the waveguide type optical nonlinear medium 2 via the light intensity varying means 8. The white pulse light output from the waveguide type optical nonlinear medium 2 is split by the optical coupler 9 and is split into the optical spectrum detecting means 1.
0, and information indicating the detected spectrum width is fed back to the light intensity varying means 8. The light intensity varying means 8 controls the light intensity of the excitation pulse light output from the pulse light source 3 so that the spectrum width of the white pulse light is maximized. The configuration in which the light intensity of the excitation pulse light is controlled by the light intensity variable means 8 is the same as in the embodiment shown in FIG. With such a configuration, the light intensity of the excitation pulse light incident on the waveguide-type optical nonlinear medium 2 is controlled to a value that maximizes the spectral width of the white pulse light, and the optical bandwidth from the waveguide-type optical nonlinear medium 2 is increased. Thus, white pulse light having high stability can be generated.

(Combination of Embodiments of Claims 1 and 2) Each embodiment of the stabilized white pulse light source of claim 1 shown in FIGS. 1 to 3 and claim 2 shown in FIGS. Each embodiment of the stabilized white pulse light source can be combined with each other. A total of six combinations are possible. For example, when the embodiment of FIG. 1 and the embodiment of FIG. 4 are combined, the pulse light source 3 is
The light intensity of the excitation pulse light is controlled by both the light intensity control means 5 and the light intensity control means 5.

When the embodiment of FIG. 2 and the embodiment of FIG. 4 are combined, the light intensity control means 5 may be separately provided to control the pulse light source 3 or the light intensity detection means 7 may be provided. May be added to the output of the optical spectrum detection means 10 and fed back to one light intensity control means 5. When the embodiment of FIG. 3 and the embodiment of FIG. 5 are combined, the light intensity varying means 8 may be separately provided to control the light intensity of the excitation pulse light, or the light intensity detecting means 7 may be provided. Output and optical spectrum detection means 1
The output of 0 may be added and one light intensity varying means 8 may be fed back.

(First of the stabilized white pulse light source of claim 3)
FIG. 6 shows a stabilized white pulse light source according to a first embodiment of the present invention. In the figure, a stabilized white pulse light source 11 has a configuration of each embodiment shown in FIGS.
This is one of the configurations based on a combination of the embodiments shown in FIGS. 3 to 3 and the embodiments shown in FIGS. White pulse light output from such a stabilized white pulse light source 11 is
Chirp (time change of instantaneous frequency of light (time derivative of phase of light)) due to wavelength dispersion of waveguide type optical nonlinear medium 2
Receive. The chirp compensating means 12 connected to the stage subsequent to the stabilized white pulse light source 11 has a group delay characteristic for canceling the chirp of the white pulse light, and compensates for the chirp of the white pulse light. As the chirp compensator 12, an optical fiber (single mode optical fiber, polarization maintaining fiber), a planar optical waveguide element, or a waveguide type diffraction grating is used.

(Second aspect of the stabilized white pulse light source of claim 3)
FIG. 7 shows a stabilized white pulse light source according to a second embodiment of the present invention. In the figure, the stabilized white pulse light source 13 has the configuration of each embodiment shown in FIGS.
In any one of the configurations according to the embodiments shown in FIGS. 3 to 3 and the embodiments shown in FIGS. 4 and 5, the chirp compensating means 12 is provided between the waveguide type nonlinear optical medium 2 and the optical coupler 9.
Is inserted. A part of the white pulse light output from the chirp compensator 12 is branched by the optical coupler 9 and input to the optical spectrum detector 10 of the stabilized white pulse light source 13. With such a configuration, the light intensity of the excitation pulse light is controlled such that the monitored chirp of the white pulse light approaches 0, and a white pulse light in which the chirp is compensated is obtained.

(First of the stabilized white pulse light source of claim 4)
FIG. 8 shows a first embodiment of a stabilized white pulse light source according to claim 4 of the present invention. In the figure, a stabilized white pulse light source 11 has a configuration of each embodiment shown in FIGS.
This is one of the configurations based on a combination of the embodiments shown in FIGS. 3 to 3 and the embodiments shown in FIGS. The spectrum of the white pulse light output from such a stabilized white pulse light source 11 has wavelength dependence. When the spectrum with respect to the wavelength λ of the white pulse light is represented by P (λ), the spectrum equalizing means 14 connected to the subsequent stage of the stabilized white pulse light source 11 is represented by C / P (λ) where C is a constant. It outputs white pulse light having transmission characteristics and a flat spectrum. As the spectrum transmitting means 14, a wavelength filter, a planar optical waveguide element, or a waveguide type diffraction grating is used.

(Second aspect of the stabilized white pulse light source of claim 4)
Embodiment 2 FIG. 9 shows a stabilized white pulse light source according to a second embodiment of the present invention. In the figure, the stabilized white pulse light source 15 has the configuration of each embodiment shown in FIGS.
In any one of the configurations of the embodiments shown in FIGS. 1 to 3 and the embodiments shown in FIGS. 4 and 5, the spectrum equalizing means 1 is disposed between the waveguide type optical nonlinear medium 2 and the optical coupler 9.
4 is inserted. Part of the white pulse light output from the spectrum equalizing means 14 is branched by the optical coupler 9 and input to the optical spectrum detecting means 10 of the stabilized white pulse light source 15. With such a configuration, white pulsed light having a flat spectrum can be obtained.

It should be noted that both the chirp compensation 12 and the spectrum equalizing means 14 may be provided.

[0027]

As described above, the stabilized white pulse light source of the present invention controls the light intensity of the excitation pulse light incident on the waveguide-type optical nonlinear medium to a value that maximizes the spectrum width of the white pulse light. Therefore, it is possible to generate white pulse light having high stability in an ultra-wide band from a waveguide type optical nonlinear medium.

Further, after the stabilized white pulse light source,
By arranging the chirp compensating means or the spectrum equalizing means, it is possible to generate white pulse light having a small chirp and a flat spectrum over a wide band.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a stabilized white pulse light source according to claim 1;

FIG. 2 is a block diagram showing a stabilized white pulse light source according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a stabilized white pulse light source according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a first embodiment of the stabilized white pulse light source according to claim 2;

FIG. 5 is a block diagram showing a second embodiment of the stabilized white pulse light source according to claim 2;

FIG. 6 is a block diagram showing a first embodiment of the stabilized white pulse light source according to claim 3;

FIG. 7 is a block diagram showing a second embodiment of the stabilized white pulse light source according to claim 3;

FIG. 8 is a block diagram showing a first embodiment of the stabilized white pulse light source according to claim 4;

FIG. 9 is a block diagram showing a stabilized white pulse light source according to a second embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of a conventional white pulse light source.

FIG. 11 is a diagram showing spectra of excitation pulse light and white pulse light.

FIG. 12 is a diagram showing the relationship between the peak intensity of excitation pulse light and the spectrum width of white pulse light.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pulse light source 2 waveguide-type optical nonlinear medium 3 pulse light source (with light intensity control function) 4,5 light intensity control means 6,9 optical coupler 7 light intensity detection means 8 light intensity variable means 10 light spectrum detection means 11,13 , 15 stabilized white pulse light source 12 chirp compensating means 14 spectrum equalizing means

Claims (4)

[Claims] 1. A white pulse light source comprising: a pulse light source for generating excitation pulse light; and a waveguide type optical nonlinear medium for generating white pulse light upon incidence of the excitation pulse light, wherein the waveguide type optical nonlinear Means for measuring in advance the relationship between the spectrum of the white pulse light generated in the medium and the light intensity of the excitation pulse light, and controlling the light intensity of the excitation pulse light so that the spectrum width of the white pulse light is maximized. A stabilized white pulse light source. 2. A white-light pulse light source comprising: a pulse light source for generating excitation pulse light; and a waveguide-type optical non-linear medium for receiving the excitation pulse light and generating white pulse light; Means for monitoring the spectrum of the white pulse light generated in the medium; and means for controlling the light intensity of the excitation pulse light so that the spectrum width of the white pulse light is maximized. White pulse light source. 3. The stabilized white pulse light source according to claim 1, further comprising means for compensating chirp of the output white pulse light. 4. The stabilized white pulse light source according to claim 1, further comprising means for equalizing the wavelength dependence of the spectrum of the output white pulse light. Pulse light source.