JPH10132579A - Light source device and optical fiber gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly precise optical fiber gyro excellent in temperature characteristic by connecting a rare earth element dope optical fiber to one end of an optical coupler, and an exciting light source and a temperature regulating device for keeping the temperature of the optical fiber constant to the other end thereof. SOLUTION: A rare earth element dope optical fiber 101A is connected to one end of a coupler 105 through an optical isolator 101C, and an exciting light source 101B is connected to the other end of the coupler 105. The optical fiber 101A has a temperature resulting function. A temperature regulating device has a constant temperature oven 201, a temperature sensor 202, a heater 203 and a control circuit 204. The optical fiber 10A, the temperature sensor 202 and the heater 203 are housed within the constant temperature oven 201. The temperature in the constant temperature oven 201 is detected by the temperature sensor 202, and this temperature signal is supplied to the control circuit 204. The control circuit 204 supplies an instruction signal to the heater 203 on the basis of the temperature signal to keep the temperature within the constant temperature oven 201 constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light source device using a rare earth element-doped optical fiber and an optical fiber gyro using the same.

[0002]

2. Description of the Related Art An interference type and a resonance type are known as optical fiber gyros for measuring an angular velocity using a Sagnac effect of light. An interference-type optical fiber gyro typically propagates light in opposite directions to one long optical path composed of an optical fiber loop, combines the two propagated lights to generate interference light, and generates the interference light. Is determined from the phase difference contained in the angular velocity.

With reference to FIG. 3, an optical fiber gyro of a phase modulation type among conventional interference types will be described. The optical fiber gyro combines a light source 101, a light receiver 102 for converting incident light into current, an optical fiber loop 103 formed by winding one optical fiber a plurality of times, a polarizer 104, and light propagating through the optical fiber. Or, couplers 105 and 106 are provided. The optical fiber gyro further includes a current / voltage converter 107, a phase modulator 108, a signal generator 109, and a synchronous detector 110.

The light output from the light source 101 passes through the first coupler 105 and the polarizer 104,
6 and is split into two lights by the second coupler 106. The two split light beams propagate through the optical fiber loop 103 in opposite directions. That is, one propagates clockwise through the optical fiber loop 103 and the other propagates counterclockwise.

When an angular velocity Ω is applied to the optical fiber loop 103, the optical fiber loop 10
3, a phase difference Δφ occurs between the lights propagating in opposite directions. This phase difference Δφ is proportional to the angular velocity Ω and is expressed by the following equation.

[0006]

## EQU1 ## Δφ = (2πLD / λC) Ω

Here, Ω is the angular velocity around the central axis of the optical fiber loop 103, D is the loop diameter of the optical fiber loop 103, L is the length of the optical fiber loop 103, and λ is the wavelength of the light beam output from the light source 101. , C represent the speed of light.

The signal generator 109 generates a reference signal having an angular frequency of ω _P and supplies it to the phase modulator 108 and the synchronous detector 110. The phase modulator 108 is the signal generator 1
The phase frequencies of the light propagating in directions opposite to each other in the optical fiber loop 103 are modulated by the angular frequency supplied from the optical fiber 09 in the optical fiber loop 103 by the reference signal of ω _P.

The phase modulator 108 is connected to the optical fiber loop 10.
3, light propagating clockwise in the optical fiber loop 103 is phase-modulated at the exit of the optical fiber loop 103, and light propagating counterclockwise is phase-modulated at the entrance of the optical fiber loop 103. You.

The lights that have propagated in the opposite directions through the optical fiber loop 103 are combined by a second coupler 106,
Interference light is generated. Such interference light is detected by the light receiver 102 via the polarizer 104 and the first coupler 105. The current signal output by the light receiver 102 is converted into a voltage signal V by the current / voltage converter 107. Such a voltage signal V is represented as follows.

[0011]

V = K [1 + cosΔφ · ｛J ₀ (z) −2J
₂ (z) cos2ω _P t + ··｝ −sinΔφ · ｛2J
_{1 (z) cosω P t- ···} }]

Here, z is the phase modulation degree, J ₀ , J ₁ , J
_2, ... are Bessel functions, K is a proportionality constant, t is time.

The synchronous detector 110 synchronously detects the voltage signal V based on the reference signal having the angular frequency ω _P supplied from the signal generator 109. As a result, the angular frequency component ω _P among the angular frequency nω _P components included in the output voltage V is synchronously detected, and the output 2KJ ₁ (z) si proportional to sinΔφ
nΔφ is output. Thus, the Sagnac phase difference Δφ
Is obtained, and the angular velocity Ω is obtained from the equation (1).

A cellodyne type optical fiber gyro is known as an improvement of the phase modulation type optical fiber gyro. In the serrodyne method, as shown in FIG.
8 'is provided. For details of the cellodyne type optical fiber gyro, refer to Japanese Patent Application No. 4-306975 filed by the same applicant as the present applicant.

Light propagating clockwise in the optical fiber loop 103 is serrodyne-modulated by a serrodyne phase modulator 108 'at the entrance of the optical fiber loop 103, and phase-modulated by the phase modulator 108 at the exit of the optical fiber loop 103. You. The light propagating counterclockwise in the optical fiber loop 103 is phase-modulated by the phase modulator 108 at the entrance of the optical fiber loop 103, and
At the exit of 03, serrodyne modulation is performed by the serrodyne phase modulator 108 '.

As the light source 101, a semiconductor light emitting device such as a light emitting diode (LED) or a super luminescent diode (SLD) is used. As the light source 101, a rare earth element doped (doped) optical fiber can be used. The rare earth elements are erbium Er, neodymium Nd,
Praseodymium Pr or the like is used.

Another example of a conventional optical fiber gyro will be described with reference to FIG. This example is disclosed in JP-A-4-98117.
The publication is disclosed in the above-mentioned publication, and the details are referred to the publication. The light source 101 is a rare earth element doped optical fiber 101A.
And an excitation light source 101B, an optical isolator 101C, and a dichroic mirror 101D. The optical fiber gyro of this example has a different configuration from the conventional optical fiber gyro shown in FIG.

The rare earth element doped optical fiber 101A may be an erbium doped optical fiber (EDF). As the excitation light source 101D, a semiconductor laser (LD) may be used. The excitation light source 101D typically has a wavelength λ = 0.
98 μm or 1.48 μm high power semiconductor laser

The excitation light from the excitation light source 101B is deflected by the dichroic mirror 101D and guided to the rare-earth element doped optical fiber 101A. The rare-earth element-doped optical fiber 101A emits light by the excitation light. Light from the rare earth element doped optical fiber 101A is guided to the first coupler 105 via the dichroic mirror 101D and the optical isolator 101C.

As described above, the light guided to the first coupler 105 is guided to the second coupler 106 via the polarizer 104, and is split into two lights. The two lights propagate through the optical fiber loop 103 in opposite directions and are combined by the second coupler 106 to generate interference light. This interference light passes through the polarizer 104 again to the second coupler 105.
And received by the light receiver 102.

The optical isolator 101C is provided to prevent light of the same wavelength in the opposite direction from propagating to the rare-earth element-doped optical fiber 101A. When the interference light is again guided to the second coupler 105, it is split into two lights, one of which is guided to the light receiver 102, and the other propagates to the light source 101 as unnecessary light. Optical isolator 101C
Is that the unnecessary light is emitted from the rare-earth element-doped optical fiber 101.
Prevent propagation to A. Thereby, the light emitting state of the rare earth element doped optical fiber 101A is stabilized.

[0022]

In the first example of FIG. 3,
As the light source 101, a semiconductor light emitting device such as a light emitting diode (LED) or a super luminescent diode (SLD) is used. The semiconductor light emitting device has a wide spectrum width (short coherent length) and has an advantage that gyro output errors can be reduced, but has a disadvantage that the wavelength of the light source changes with temperature. Typically, the rate of temperature change of the wavelength λ of the light source is about 300 ppm / ° C.
It is. In addition, there is a disadvantage that the amount of light that can be coupled to the optical fiber is relatively small and cannot be used for a high-precision optical fiber gyro.

In the second example shown in FIG. 4, a rare earth element-doped optical fiber is used as the light source 101. This light source has a wavelength λ
Has a relatively small temperature change, and has an advantage that it can be easily coupled to the optical fiber end on the sensor side of the optical fiber gyro.

However, temperature characteristics are not sufficient in certain applications, particularly in a measuring device requiring high accuracy, for example, a high-precision optical fiber gyro.

In view of the above, an object of the present invention is to provide a light source using a rare earth element-doped optical fiber having excellent temperature characteristics.

In view of the foregoing, an object of the present invention is to provide a high-precision optical fiber gyro having an RDF light source having excellent temperature characteristics.

[0027]

According to the present invention, in a light source device, a rare earth element-doped optical fiber connected to one end of an optical coupler, an excitation light source connected to the other end of the optical coupler, and A temperature controller for maintaining the temperature of the rare-earth element-doped optical fiber constant, wherein light of the first wavelength from the excitation light source enters the rare-earth-element-doped optical fiber via the optical coupler. The light of the second wavelength is emitted from the rare-earth element-doped optical fiber to the other end of the optical coupler.

According to the present invention, in the light source device, the temperature control device has a thermostatic chamber for accommodating the rare earth element-doped optical fiber. Further, the temperature control device includes a temperature sensor and a heater responsive to a signal from the temperature sensor. The temperature sensor and the heater and the rare earth element-doped optical fiber are wound on the same bobbin. The rare earth element-doped optical fiber is coated with a heating element, and the heat generated by the heating element is configured to maintain the rare earth element-doped optical fiber at a constant temperature.

According to the present invention, there are provided a light source, a light receiver, two couplers for combining and branching light, and an optical fiber loop,
The light from the light source passes through a first coupler and is split into two lights by a second coupler, and the two lights propagate through the optical fiber loop in opposite directions to each other and are combined by the second coupler. An optical fiber gyro configured to generate interference light and receive the interference light by the light receiver via the first coupler, wherein the light source is connected to one end of the first coupler. A rare earth element-doped optical fiber; an excitation light source connected to the other end of the first coupler; and a temperature controller for keeping the temperature of the rare earth element-doped optical fiber constant. Further, the first coupler can reduce the input light by approximately 5 irrespective of the wavelength of the input light.
It is configured to split into two lights at a ratio of 0:50.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. The optical fiber gyro of this example has a rare earth element doped optical fiber 101A and a pumping light source 101B as light sources. Rare earth element doped optical fiber 10
1A is connected to one end of the first coupler 105 via the optical isolator 101C, and the excitation light source 101B is connected to the other end of the first coupler 105. The rare-earth element doped optical fiber 101A has a temperature control function.

The light source of the optical fiber gyro of this embodiment is shown in FIG.
As compared with the light source of the second conventional example described with reference to
Excitation light source 1 using dichroic mirror 101D
01B from rare earth element doped optical fiber 101A
Instead, the light from the excitation light source 101B is guided to the rare-earth element-doped optical fiber 101A via the optical fiber end of the first coupler 105. The difference is that an adjustment function is provided.

The optical fiber gyro of this embodiment has the same configuration as the first and second examples of the conventional optical fiber gyro shown in FIGS. 3 and 4 except for the configuration of the light source. That is,
A photodetector 102 for converting incident light into a current, an optical fiber loop 103 formed by winding one optical fiber a plurality of times, a polarizer 104, and couplers 105 and 106 for synthesizing or splitting light propagating through the optical fiber. And a current / voltage converter 107, a phase modulator 108, a signal generator 109, and a synchronous detector 110.

A description will be given of the temperature control device provided in the rare-earth element doped optical fiber 101A. The temperature control device of this example includes a constant temperature box 201, a temperature sensor 202, and a heater 2.
03 and a control circuit 204. Although not shown, an appropriate power supply is connected to the temperature sensor 202 and the heater 203.

The rare-earth element-doped optical fiber 101 A, the temperature sensor 202 and the heater 203 are housed in a thermostat box 201. Constant temperature box 201 by temperature sensor 202
Is detected, and this temperature signal is supplied to the control circuit 204. The control circuit 204 generates a command signal based on the temperature signal and supplies the command signal to the heater 203. In this way, the heater 203 operates, and the temperature in the constant temperature box 201 is kept constant.

A second example of the temperature control device will be described with reference to FIG. In the example shown in FIG. 2A, the rare earth element doped optical fiber 101A and the temperature sensor 20
2 and the heater 203 are wound. In the example shown in FIG. 2B, a rare earth element doped optical fiber 301 and a temperature sensor 202 are wound around a bobbin 300. The coated rare earth element doped optical fiber 301 has a configuration in which a heating element is coated on the outside of the rare earth element doped optical fiber 101A.

Although not shown in FIG. 2, the bobbin 30
0 may be stored in the thermostat box 201. In the example of FIG. 2A, a control circuit 204 is connected between the temperature sensor 202 and the heater 203, and in the example of FIG.
A control circuit 204 is connected between the heating element 02 and the heating element.
Further, an appropriate power supply is connected to the heater 203 and the heating element.

When the heating element itself is a self-temperature control type heating element having a temperature control function, the temperature sensor 2
02 is removed. The self-temperature control type heating element is designed such that when the temperature decreases, the electric resistance increases and the calorific value increases, and when the temperature increases, the electric resistance decreases and the calorific value decreases. Is configured. Not only when the temperature changes as a whole but also when the temperature changes locally, the temperature is always kept constant by the self-temperature control action.

Although the embodiments of the present invention have been described in detail, it will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments and can adopt various other configurations without departing from the spirit of the present invention. It will be easily understood.

[0039]

According to the present invention, the rare-earth-element-doped optical fiber is always maintained at a constant temperature by the temperature control device, so that there is an advantage that a highly accurate light source device can be provided.

According to the present invention, since the light source device is provided with the temperature control device and can always provide light of a constant intensity, there is an advantage that a highly accurate optical fiber gyro can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an optical fiber gyro of the present invention.

FIG. 2 is a diagram showing a main part of the light source device of the present invention.

FIG. 3 is a diagram showing a first example of a conventional optical fiber gyro.

FIG. 4 is a diagram showing a second example of a conventional optical fiber gyro.

[Explanation of symbols]

 Reference Signs List 101 light source 101A rare earth element doped optical fiber 101B excitation light source 101C optical isolator 101D dichroic mirror 102 light receiver 103 optical fiber loop 104 polarizer 105,106 coupler 107 current-voltage converter 108,108 'phase modulator 109 signal generator 110 synchronization Detector 201 Thermostatic box 202 Temperature sensor 203 Heater 204 Control circuit 300 Bobbin 301 Rare earth element doped optical fiber with film

Claims (7)

[Claims] 1. A rare earth element-doped optical fiber connected to one end of an optical coupler, an excitation light source connected to the other end of the optical coupler, and a temperature for maintaining the temperature of the rare earth element doped optical fiber constant. A light of a first wavelength from the excitation light source is incident on the rare-earth element-doped optical fiber via the optical coupler, and a second wavelength of light is emitted from the rare-earth element-doped optical fiber. A light source device configured to emit light to the other end of the optical coupler. 2. The light source device according to claim 1, wherein said temperature control device has a constant temperature chamber for accommodating said rare earth element-doped optical fiber. 3. The light source device according to claim 1, wherein the temperature control device includes a temperature sensor and a heater responsive to a signal from the temperature sensor. 4. The light source device according to claim 3, wherein the temperature sensor and the heater and the rare earth element-doped optical fiber are wound around the same bobbin. 5. The light source device according to claim 1, wherein the rare-earth element-doped optical fiber is coated with a heating element, and the rare-earth element-doped optical fiber is maintained at a constant temperature by the heat generated by the heating element. A light source device, characterized in that: 6. A light source, a light receiver, and two couplers for combining and splitting light and an optical fiber loop, and light from the light source passes through a first coupler and is split into two lights by a second coupler. The two lights propagate through the optical fiber loop in opposite directions, and are combined by the second coupler to generate interference light. The interference light is transmitted by the light receiver via the first coupler. In the optical fiber gyro configured to receive light, the light source is a rare earth element doped optical fiber connected to one end of the first coupler, the excitation light source connected to the other end of the first coupler, and An optical fiber gyro, comprising: a temperature control device for maintaining a temperature of a rare earth element-doped optical fiber constant. 7. The optical fiber gyro according to claim 6, wherein the first coupler is configured to split the input light into two lights at a ratio of approximately 50:50 regardless of the wavelength of the input light. An optical fiber gyro characterized by the above.