JP3344877B2 - Pulse laser device and OTDR device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a pulse laser device for generating pulse laser light in a narrow wavelength range, and an OTDR device using the pulse laser device.

[0002]

2. Description of the Related Art In a conventional pulse laser apparatus for generating pulse laser light in a narrow wavelength range, a logic "0" is changed to a logic "1" by combining a Fabry-Perot type semiconductor laser and an optical waveguide type diffraction grating. By supplying a pulsed drive current to the Fabry-Perot semiconductor laser, pulse modulation oscillation is performed.

That is, an optical waveguide type diffraction grating having reflection wavelength selectivity is disposed opposite to an optical output position of a Fabry-Perot type semiconductor laser, and a part of light emitted from the Fabry-Perot type semiconductor laser is converted by the optical waveguide type diffraction grating. By repeatedly reflecting and returning to the laser medium of the Fabry-Perot type semiconductor laser, pulsed laser light in a narrow wavelength range substantially equal to the selected wavelength of the optical waveguide type diffraction grating is stimulated to be emitted.

Further, as shown in FIG. 5 (a), the drive current is set to a current value that can excite stimulated emission when the logic is "0" and 0 ampere and when the logic is "1".

In the conventional OTDR device, a pulse laser beam emitted from the pulse laser device having such a structure is incident on an optical fiber transmission line or the like, which is a subject, thereby causing backscattering occurring at various parts in the optical fiber. By detecting the light, the presence or absence of an abnormality in the optical fiber transmission line and the location of the abnormality are detected. By applying the above pulse laser device, the narrowest wavelength range (half width) is about 30 n.
The measurement was performed with m pulse laser light.

[0006]

However, in the above-mentioned conventional pulse laser device, a pulse-like drive current which reverses from 0 ampere to a predetermined current value as shown in FIG. When the laser light is excited by the pulsed drive current, the light emitted from the laser medium immediately after supplying the pulsed drive current has a wide wavelength range, and at least this light is wavelength-selected by the optical waveguide type diffraction grating. During the period until the laser medium returns to the laser medium again, there is a problem that pulse laser light in a desired narrow wavelength range cannot be obtained. That is, as shown in the spectrum distribution of FIG.
During a certain period from time t ₀ immediately after supplying the pulsed drive current, light in a wide wavelength range is emitted, and then pulsed laser light in a desired narrow wavelength range is emitted. There was a problem with the stability of the region. FIG. 5B shows a change in the spectrum distribution with the passage of time, and the Z axis in the figure shows the light intensity at each wavelength.

Further, the OTDR apparatus has a problem that it is not possible to inspect an optical fiber transmission line with high accuracy with light in a wide wavelength range as described above. For example, as a function of an OTDR device, a point in time when pulsed laser light is introduced from a pulsed laser device to an optical fiber transmission line or the like (for example,
The point in time when backscattered light is detected from t ₁ ) (for example, t ₂ )
Has the function of measuring the time (= t ₂ −t ₁ ) and determining the distance to the abnormality occurrence site based on the measured time. If the light is not light, the detection time t ₁ will fluctuate, etc., which will cause problems such as hindering improvement in measurement accuracy. In addition, since it is difficult to perform measurement in synchronization with the point in time when the pulse-shaped drive current is supplied, there is another problem that it is difficult to set measurement timing.

The present invention has been made in view of the above problems, and provides a pulse laser device having high responsiveness and high stability with respect to a wavelength range. An object of the present invention is to provide an OTDR device that enables high-precision measurement with a pulse laser beam of 30 nm or less.

[0009]

According to a first aspect of the present invention, there is provided a pulse laser apparatus, wherein a Fabry-Perot laser and a light emitting end of the Fabry-Perot laser are provided continuously.
An optical waveguide type diffraction grating that selectively reflects a part of light having a predetermined wavelength emitted from the Fabry-Perot laser and returns the light to the Fabry-Perot laser, and guides the remaining light to an output side; The laser is provided with a drive unit for supplying a pulsed pulse current required for generating pulsed laser light, after supplying a stabilizing current equal to or higher than the oscillation threshold current to the laser for a predetermined period. Further, the drive unit may supply the pulse current to the Fabry-Perot laser before the laser beam reciprocates in the resonator of the Fabry-Perot laser any number of times from 1 to 200 times. It is characterized in that the stabilized current is supplied.

[0010] Thus, by supplying a stabilizing current during a period in which the laser beam reciprocates one or two times in the resonator of the Fabry-Perot laser, the stimulated emission of the laser beam is reduced. Stabilize well. Therefore, in the Fabry-Perot laser, the laser oscillation operation is stabilized by the stabilizing current before the pulse current is supplied and the pulsed laser beam is emitted. Is emitted.

According to a second aspect of the present invention, in the pulse laser device, the driving unit according to the first aspect sets a ratio of a current value between the pulse current and the stabilizing current to about 10: 1 or more. And According to this, the light intensity of the light component generated with the supply of the stabilizing current is reduced from the light intensity of the pulse laser light that is originally required, and the laser light with good SN is emitted.

According to a third aspect of the present invention, there is provided an OTDR device, comprising: a Fabry-Perot laser; An optical waveguide type diffraction grating for selectively reflecting a portion to return to the Fabry-Perot laser and guiding the remaining light to an output side; and a stabilizing current equal to or higher than the oscillation threshold current of the Fabry-Perot laser. And a drive unit for supplying a pulsed pulse current required for pulsed laser light generation after supplying the laser beam for a predetermined period, and the remaining light guided through the optical waveguide type diffraction grating as strobe light to the subject. And a measuring unit for measuring reflected light from the subject while being incident. Further, the drive unit may supply the pulse current to the Fabry-Perot laser before the laser beam reciprocates in the resonator of the Fabry-Perot laser any number of times from 1 to 200 times. It is characterized in that the stabilized current is supplied.

[0013] By supplying a stabilizing current during a period in which the laser beam reciprocates one to 200 times in the cavity of the Fabry-Perot laser, the stimulated emission of the laser beam is reduced. Stabilize well. Therefore, the subject is measured with high accuracy by emitting pulse laser light (strobe light) in a narrow wavelength range immediately after the pulse current is supplied from the Fabry-Perot laser.

According to a fourth aspect of the present invention, in the OTDR device, the driving unit according to the third aspect sets a ratio of a current value between the pulse current and the stabilizing current to about 10: 1 or more. did. Also in this case, the subject is measured with high accuracy by emitting pulse laser light (strobe light) in a narrow wavelength range immediately after the pulse current is supplied from the Fabry-Perot laser.

According to a fifth aspect of the present invention, in the OTDR device, the measuring unit according to the third aspect includes an offset removing circuit for removing a DC component in the reflected light or an AC coupling circuit having a low-pass removing filter. A configuration was provided. According to this, the DC component in the reflected light caused by the light component generated by the supply of the stabilizing current being included in the strobe light is removed, so that substantially only the pulse laser light is removed. Information on reflected light obtained as strobe light is obtained, and the subject is measured with high accuracy.

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) An embodiment of a pulse laser device according to the present invention will be described with reference to FIGS. First, the device configuration will be described with reference to FIG.
A Fabry-Perot laser in which light reflecting surfaces 4 and 6 are disposed opposite to each other on a laser medium 2 made of a semiconductor having a heterostructure of GaAsP / InP or the like is provided. One light reflecting surface 4 has a high reflectance of, for example, about 80%, and the other light reflecting surface 6 has a low reflectance of, for example, about 5%. The light is transmitted through the reflection surface 6 and emitted.

The condenser lens 8 faces the light reflecting surface 6.
Are disposed opposite to each other, and the end face of the core of the optical fiber 10 on which the optical waveguide type diffraction grating 12 described later is formed is disposed behind the condenser lens 8. Note that both the emission position of the laser light and the end face of the core of the optical fiber 10 are arranged so as to coincide with the optical axis of the condenser lens 8.

The optical waveguide diffraction grating 12 is, as shown in an enlarged longitudinal sectional view in the figure, a part of a core 14 provided in a clad 16 of the optical fiber 10 to which ultraviolet light or the like is applied along a light guiding direction. By irradiating, a plurality of refractive index changing portions (striped portions in the drawing) having a refractive index n ₂ (in this embodiment, n ₁ <n ₂ ) different from the original refractive index n ₁ of the core 12. ) Is formed. That is, the portions of the refractive indices n ₁ and n ₂ along the optical waveguide direction have a predetermined pitch Δ
, And has a so-called refractive index change distribution that changes periodically, and exhibits wavelength selectivity of selectively reflecting light having a wavelength of λ = 2n ₁ Δ among light transmitted through the refractive index change distribution. That is, when the incident light is introduced from one end of the core 12 (the side facing the condenser lens 8), the light having the wavelength λ returns to the condenser lens 8 side as reflected light due to the wavelength selectivity of the optical waveguide diffraction grating 12, and the wavelength λ Are output to the other end as emission light. Here, the light transmittance of the optical waveguide diffraction grating 12 is set to about 47%.

The other end of the optical fiber 10 is provided with an optical connector 18 for coupling to another optical fiber or the like.

A drive section 20 for supplying a drive current (electric power) I for excitation to the laser medium 2 and a timing control circuit 22 for controlling the output timing of the drive current I
Is provided. The drive unit 20 has a stabilized power generation circuit 24 that outputs a stabilized current (power) Is for stabilizing laser oscillation, which will be described later, and a pulse power generation circuit 26 that outputs a pulse current (power) Ip. And these circuits 2
The timing control circuit 22 controls the output timings of the currents Is and Ip at 4 and 26.

Further, the driving unit 20 has the above-mentioned currents Is and Ip
Are added to supply a driving current I (= Is + Ip) to the laser medium 2.

Next, the operation of the pulse laser device having such a configuration will be described with reference to FIGS. As shown in FIG. 2A, the stabilized power generation circuit 24 in the drive section 20 continuously outputs a constant current of a certain value under the control of the timing control circuit 22 to generate pulse power. The circuit 26
According to a control signal at a predetermined timing from the timing control circuit 22, a pulse-like pulse current Ip as shown in FIG.

The pulse current Ip is supplied to the timing control circuit 2
The current is 0 amperes during the period not indicated by the control signal from the control signal 2, and at the time point indicated by the control signal, the current value Im is set to a sufficient current value to excite the laser medium 2. The current value of the stabilizing current Is is set to a constant current value of about 1/10 of the current value Im, that is, Im / 10. The current value of the stabilization current Is is
The threshold current required for the Fabry-Perot laser to cause laser oscillation is set to a value equal to or higher than the threshold current. Then, these currents Is and Ip are added by the current adding circuit 28, so that a driving current I (= Is + Ip) as shown in FIG. 2C is supplied to the laser medium 2.

When the driving current I becomes the stabilizing current Is (= Im / 1)
0), the light excited by the laser medium 2 by the current Is is introduced into the core 14 of the optical fiber 10 through the light reflecting surface 6 or the condenser lens 8,
Further, a part of the light having the reflection wavelength (Bragg wavelength) λ set in the optical waveguide type diffraction grating 12 is reflected and reenters the laser medium 2 via the condenser lens 8 or the light reflection surface 6, and the light reflection surface 4 and 6 contribute to stimulated emission accompanying the phenomenon of interference. Further, the stimulated emission light is introduced into the core 14 of the optical fiber 10 through the light reflecting surface 6 or the condenser lens 8 and the reflection wavelength (Bragg wavelength) λ of the optical waveguide type diffraction grating 12 is set. Part of the light is reflected and again enters the laser medium 2 via the condenser lens 8 or the light reflecting surface 6 and contributes to the stimulated emission. Therefore, a laser beam having a wavelength equal to the reflection wavelength λ set in the optical waveguide type diffraction grating 12 is emitted from the Fabry-Perot laser due to the above-mentioned stimulated emission phenomenon occurring continuously. However, since the drive current I during this period is the stabilization current Is (= Im / 10), the light intensity of the laser light emitted during this period is
The intensity becomes lower than the desired intensity of the pulsed laser light. More specifically, since the relation of Is = Im / 10 is set, the intensity is lower by -10 dB than the intensity of the desired pulsed laser light.

Next, when the pulse current Ip is generated during the drive current I, a pulsed laser light having a high light intensity is emitted from the Fabry-Perot laser with the sharp rise of the drive current I, and the condenser lens 8 Or optical fiber 1
0 and output as output light via the optical connector 18.

FIG. 2D schematically shows a measurement result obtained by actually measuring the change in the spectrum distribution of the outgoing light output from the optical connector 18 with the passage of time. The light intensity is shown on the Z axis. I have. According to this, during the period in which the drive current I becomes the stabilization current Is (= Im / 10), laser light with a small light intensity at the wavelength λ is generated, and the pulse current I
When p was supplied, it was confirmed that the light was generated in the form of a pulse having a large light intensity at the wavelength λ. Actually, a laser beam having a wavelength band having a half-value width of about 0.3 nm with the wavelength λ as a central wavelength was able to be realized.

Further, the supply interval of the pulse currents Ip adjacent to each other (in other words, the period during which only the stabilizing current Is is supplied) is at least the light emitted from the laser medium 2 is the optical waveguide type diffraction grating 12. It is necessary to set a period (a period of one round trip) until the light is reflected by and contributes to the return stimulated emission. According to the measurement results, when the pulse current Ip was supplied at the time when the stabilization current Is was continuously supplied for about 200 round-trip periods, it was possible to output a pulse laser beam in a very stable and narrow wavelength range.

As described above, according to this embodiment, the laser oscillation is preliminarily generated by supplying the stabilized current Is to the Fabry-Perot type laser before generating the pulse laser light in the narrow wavelength range originally required. Since pulsed laser light is supplied in the desired narrow wavelength range when the pulse current Ip is supplied, the responsiveness is extremely good and stable in the narrow wavelength range as compared with the prior art. A pulse laser device having extremely good performance can be provided. That is, in the prior art, as shown in the spectrum distribution of FIG. 5A, immediately after the pulse current is supplied to the pulse laser device, light in a wide wavelength range is generated, and the pulse laser light in a desired narrow wavelength range is generated. However, the pulse laser device according to the present embodiment has an excellent effect that a stable pulsed laser beam in a narrow wavelength range can be obtained immediately after the pulse current is supplied.

Further, only the stabilizing current Is is applied to the laser medium 2.
The laser light is also output during the period of supplying the laser light, which becomes a noise light component.
By setting s to a value smaller than the pulse current Ip, this noise light component can be made smaller than the desired light intensity of the pulsed laser light, so that it has been applied to various optical devices and optical communication fields. Even in this case, it is not a substantial problem.

The drive section 20 of this embodiment is provided with a stabilized power generation circuit 24 and a pulse power generation circuit 26 independently to output a stabilized current Is and a pulse current Ip. Although the driving current I is generated by adding the currents Ip to each other, the present invention is not limited to the case where such independent circuits 24 and 26 are provided, for example, as shown in FIG. A driving unit that directly outputs the driving current I having the waveform shown in FIG.

(Second Embodiment) Next, a second embodiment of the pulse laser device will be described with reference to FIG. The configuration of this device is basically the same as that of the pulse laser device shown in FIG. 1, so that the description thereof will be omitted and the differences will be described in detail.

The stabilized power generation circuit 24 shown in FIG. 1 responds to a control signal from the timing control circuit 22 according to FIG.
As shown in the figure, a rectangular stabilizing current Is is output. Further, the pulse power generation circuit 26 includes the timing control circuit 2
In response to the control signal from the control unit 2, a pulsed pulse current p is output as shown in FIG. Here, the time width (generation period) of each stabilization current Is is longer than the time width of the pulse current p, and the stabilization current Is is output synchronously a certain time before the output point of the pulse current Ip. Timing control is performed.

Therefore, the drive current I (= Is + Ip) supplied to the laser medium 2 in FIG. 1 changes to a stepped state as shown in FIG. 3 (c). The pulse current Ip is 0 amperes during a period not instructed by the control signal from the timing control circuit 22. At a point in time instructed by the control signal, a current value sufficient to excite the laser medium 2 is obtained. Im. The current value of the stabilizing current Is is about 1/10 of the current value Im, that is, Im / 1.
It is set to a constant current value of zero. Also, the stabilizing current I
The current value of s is set to a current value that is not necessary for the Fabry-Perot type laser to cause laser oscillation or a current value higher than that.

When the driving current I having the waveform shown in FIG. 3C is supplied to the Fabry-Perot laser shown in FIG. 1, during the period in which only the stabilizing current Is is supplied, the optical waveguide type diffraction grating 12 has a small light intensity but has a small light intensity. Is output and the drive current I, which is the sum of the pulse current Ip and the stabilization current Is, is supplied, the light intensity is high and the pulse in the narrow wavelength region of the center wavelength λ is supplied. Laser light is output.

FIG. 3D schematically shows a measurement result obtained by actually measuring a change in the spectrum distribution of the outgoing light output from the optical connector 18 of FIG. 1 with the passage of time. Indicated by. According to this, immediately after the drive current I rises from 0 amps to Im / 10 (in other words, immediately after the stabilization current Is rises from 0 amps to Im / 10), the wide wavelength After the elapse of the period, a laser beam having a small wavelength λ is output, and when the pulse current Ip is supplied, the laser beam has a high light intensity and a narrow wavelength of the central wavelength λ. It was confirmed that the desired pulsed laser light in the range was output. In practice, a pulse laser beam having a half-width of about 0.3 nm with the wavelength λ as the center wavelength could be realized.

Further, a period during which the stabilizing current Is is supplied before the pulse current Ip is supplied (in other words, the stabilizing current I
The period during which only s is supplied) is a period (at least one round-trip period) until at least light emitted from the laser medium 2 is reflected by the optical waveguide type diffraction grating 12 and contributes to the return stimulated emission.
However, if the pulse current Ip is supplied at the time when the stabilization current Is is continuously supplied over about 200 round-trip periods, it is possible to output a pulse laser beam in a very stable and narrow wavelength range. Confirmed experimentally.

As described above, according to this embodiment, although light in a wide wavelength range is slightly generated, the responsiveness is very good and the stability in a narrow wavelength range is very good as compared with a conventional laser device. A simple pulse laser device can be provided.

Further, only the stabilizing current Is is applied to the laser medium 2.
The laser light is also output during the period of supplying the laser light, which becomes a noise light component.
By setting s to a value smaller than the pulse current Ip, this noise light component can be made smaller than the desired light intensity of the pulsed laser light, so that it has been applied to various optical devices and optical communication fields. Even in this case, it is not a substantial problem.

The drive section 20 of this embodiment is provided with a stabilized power generation circuit 24 and a pulse power generation circuit 26 independently of each other to output a stabilized current Is and a pulse current Ip. Although the driving current I is generated by adding the currents Ip, the present invention is not limited to the case where such independent circuits 24 and 26 are provided. For example, FIG. A driving unit that directly outputs the driving current I having the waveform shown in FIG.

(Third Embodiment) Next, an embodiment of an OTDR device according to the present invention will be described with reference to FIG. still,
In FIG. 4, the same or corresponding parts as those in FIG. 1 are denoted by the same reference numerals.

This OTDR device includes the Fabry-Perot laser LD shown in FIG. 1, the drive section 20 shown in FIG. 1, and a timing control circuit 30 provided in a microcomputer system or the like. The timing control circuit 30 outputs a control signal to the drive section 20 to supply the Fabry-Perot laser 28 with the drive current I having the waveforms shown in FIGS. 2C and 3C. , And also outputs a signal for controlling the operation timing of the entire OTDR device.

A condenser lens 8 is arranged to face the light emitting end of the Fabry-Perot type laser LD, and further behind the condenser lens 8, the core end of the optical fiber 10 on which the optical waveguide type diffraction grating 12 is formed faces. Thus, the pulse laser device shown in FIG. 1 is realized.

One end of the optical fiber 10 is provided with a bidirectional optical branching coupler 34 for optically coupling with another optical fiber (hereinafter referred to as an introduction fiber) 32 for guiding measurement light, which will be described later. I have. An optical connector 36 is provided at the end of the optical fiber 10, and the optical fiber transmission line 3 to be inspected is provided.
8 and the like are connected to the optical connector 36.

One end of the introduction fiber 32 is terminated by a non-reflective material or the like for suppressing the reflection of light, and the other end is connected to a measuring unit having the following components 40 to 52.

That is, the other end of the introduction fiber 32 is connected to a photodetector 40 having a photoelectric conversion element for photoelectrically converting the measurement light guided through the branch coupler 34.
The photodetector 40 includes an amplifying circuit 42 for amplifying a photoelectric conversion signal which is an output signal thereof, and an AC coupling including an offset removing circuit for removing a DC component in a signal output from the amplifier 42 and a low-frequency removing filter. A for converting a signal passing through the circuit 44 and the AC coupling circuit 44 into digital data
/ D converter 46, and an integrated averaging circuit 48 that integrates the digital data at a predetermined operation cycle to calculate a time average value
A logarithmic conversion circuit for logarithmically converting the time average value output from the integrating and averaging circuit 48, and a display unit 52 for displaying the logarithmic value data output from the logarithmic conversion circuit 50 on a CRT display or the like by various graphic processes. And are cascaded.

The A / D conversion timing of the A / D converter 46 and the operation cycle of the integration and averaging circuit 48 are controlled by the timing control circuit 30. These timings are further controlled by the drive current I in the Fabry-Perot laser LD. Is synchronized with the timing at which the pulse laser light in the narrow wavelength range is emitted from.

Next, the operation of the OTDR device having such a configuration will be described. By supplying the drive current I having the waveform shown in FIG. 2 (c) or FIG. 3 (c) to the Fabry-Perot type laser LD, pulse laser light in a narrow wavelength range is emitted.
Alternatively, the light is introduced into the optical fiber transmission line 38 via the branch coupler 34 and the optical connector 36. That is, the pulse laser light hv ₁ of the narrow wavelength band is the strobe light for inspecting the presence or absence of abnormality in the optical fiber transmission line 38.

[0061] In the optical fiber transmission line 38, back-scattered light, and the like that travels in the opposite direction (the optical coupler 36 side) is generated by Rayleigh scattering, introducing such light through the measurement light hv ₂ next optical branching coupler 34 Fiber 32 Wave guiding to

Then, the photodetector 40 photoelectrically converts the measurement light hν ₂ , the amplifier 42 amplifies this photoelectrically converted signal, and removes an unnecessary DC component by the AC coupling circuit 44, and supplies the converted signal to the A / D converter. Supplied and converted to digital data. Further, by integrating the digital data in the integrating and averaging circuit 48 and calculating the average value, optical power indicating the degree of abnormality in the optical fiber transmission line 38 and the distance to the site where the abnormality occurs is extracted, and further logarithmic conversion is performed. Circuit 50
The result of the logarithmic conversion of the average value is displayed on the display unit 52, thereby indicating the result of the abnormality inspection of the optical fiber transmission line 38.

According to the OTDR apparatus, the object to be measured is measured with the pulse laser light in an extremely narrow wavelength range as the strobe light hν ₁ , so that the distance to the abnormality occurrence site in the object to be measured can be precisely measured, High measurement is possible.

[0064]

As described above, according to the pulse laser device of the present invention, in order to emit the originally required pulse laser light from the Fabry-Perot laser, it is necessary to supply the pulse current to the Fabry-Perot laser instead of supplying the pulse current to the Fabry-Perot laser. Before, a stabilizing current is supplied in advance during a period in which the laser beam reciprocates one or two times in the resonator of the Fabry-Perot laser, so that the Fabry-Perot laser is controlled by the stabilizing current. It becomes a stable laser oscillation state in advance,
Immediately after the supply of the pulse current, stable pulse laser light in a narrow wavelength range can be obtained. In addition, according to actual measurement, a pulse laser beam in a narrow wavelength range of about 0.3 nm can be obtained, and an excellent effect is exhibited when applied to various measuring devices, for example.

According to the OTDR device of the present invention, by applying the above-described pulse laser device of the present invention as a light source, there is an excellent effect that a subject can be measured with high accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a first embodiment of a pulse laser device according to the present invention.

FIG. 2 is an explanatory diagram for explaining the operation and principle of the first embodiment.

FIG. 3 is an explanatory diagram for explaining the operation and principle of a pulse laser device according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a schematic configuration of an OTDR device according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram for explaining a problem of a conventional pulse laser device.

[Explanation of symbols]

2 laser medium, 4 6 light reflecting surface, 8 condenser lens, 10 optical fiber, 12 optical waveguide type diffraction grating,
14 core, 16 clad, 18 optical connector, 20
... Drive unit 22, 22 timing control circuit, 24 stabilized power generation circuit, 26 pulse power generation circuit, 28 current addition circuit, 30 timing control circuit, 32 introduction fiber, 34 branch coupler, 36 light Coupler, 40 photodetector, 42 amplifier, 44 AC coupling circuit, 46 A / D
Converter, 48: integrating and averaging circuit, 50: logarithmic circuit, 52
... Display unit, LD ... Fabry-Perot type laser.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-5961 (JP, A) JP-A-1-162392 (JP, A) JP-A-63-184 (JP, A) JP-A-6-196 13688 (JP, A) JP-A-5-322695 (JP, A) JP-A-6-148326 (JP, A) Laser Focus 23 [10] (1987) p. 142, 144, 147 (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 5/00-5/50 H01M 11/00 JICST file (JOIS)

Claims (5)

(57) [Claims] 1. A Fabry-Perot laser that is connected to a light emitting end of the Fabry-Perot laser and selectively reflects a part of light having a predetermined wavelength emitted from the Fabry-Perot laser. Returning to the laser, and an optical waveguide type diffraction grating for guiding the remaining light to the output side; and supplying the Fabry-Perot laser with a stabilizing current not less than its oscillation threshold current for a predetermined period. And a driving unit that supplies a pulsed pulse current required for generating pulsed laser light, wherein the driving unit supplies the Fabry-Perot laser to the Fabry-Perot laser before supplying the pulse current. Supplying the stabilizing current during a period in which the laser beam reciprocates any number of times from 1 to 200 times. 2. The pulse laser device according to claim 1, wherein the drive unit sets a ratio of a current value of the pulse current to a value of the stabilization current to about 10: 1 or more. 3. A Fabry-Perot laser that is connected to a light emitting end of the Fabry-Perot laser and selectively reflects a part of light having a predetermined wavelength emitted from the Fabry-Perot laser. Returning to the laser, and an optical waveguide type diffraction grating for guiding the remaining light to the output side; and supplying the Fabry-Perot laser with a stabilizing current not less than its oscillation threshold current for a predetermined period. A driving unit for supplying a pulsed pulse current required for generating pulsed laser light, and the remaining light guided through the optical waveguide type diffraction grating is incident on the subject as strobe light, and reflected light from the subject is reflected from the subject. And a measuring unit for measuring the following. The driving unit, before supplying the pulse current to the Fabry-Perot laser, feeds the laser through the resonator of the Fabry-Perot laser. Light supplying the stabilizing current during any period that the number reciprocation of the one and 200 times, OTDR apparatus characterized by. 4. The OTDR device according to claim 3, wherein the driving unit sets a ratio of a current value between the pulse current and the stabilization current to about 10: 1 or more. 5. The OTDR device according to claim 3, wherein the measuring unit includes an offset removing circuit for removing a DC component in the reflected light or an AC coupling circuit having a low-pass removing filter.