JP2010043984A - Light wavelength measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light wavelength measuring device for having a stable temperature characteristic in a wide outer temperature range by using a function of a phase compensator having a refractive index temperature dependency. <P>SOLUTION: This light wavelength measuring device includes a main beam splitter that splits a light beam to be measured into a first split light beam and a second split light beam and causes the first and second split light beams passing through different optical paths to be interfered with each other. The light wavelength measuring device further includes a wavelength plate that is disposed on at least one of the optical paths of the first and second split light beams, the phase compensator that is disposed on at least one of the optical paths of the optical paths of the first and second split light beams and has the refractive index temperature dependency, a polarized light beam splitter that splits interference light obtained by the above interfering in accordance with the polarization state, and a light sensing element that receives the interference light split by the polarized light beam splitter. The light wavelength measuring device includes a heating means attached to the phase compensator and a control circuit that controls temperature of the phase compensator by way of the heating means on the basis of the ambient temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  According to the present invention, the light to be measured is split into a first branched light and a second branched light by a main beam splitter, and the first branched light and the second branched light are transmitted by the main beam splitter via different optical paths. A wave plate disposed on at least one of the optical path of the first branched light and the optical path of the second branched light, and at least one of the optical path of the first branched light and the optical path of the second branched light A phase compensator having a refractive index temperature dependency disposed on the optical path, a polarization beam splitter for branching the interference light obtained by the interference according to the polarization state, and the interference light branched by the polarization beam splitter And a light wavelength measuring device including the light receiving element.

  An optical wavelength measuring device equipped with a Michelson interferometer that divides the light to be measured into two and combines them again is a well-known technique disclosed in Patent Document 1. A temperature compensation method using a phase compensator having a refractive index temperature dependency arranged on the optical path of a Michelson interferometer is also a well-known technique.

  FIG. 2 is a functional block diagram of a wavelength tunable laser light source using an optical wavelength measuring device using a Michelson interferometer as a wavelength monitor. Laser light R0 transmitted from the variable wavelength laser light source 10 passes through the beam splitter 20 to give output light R1, and reflected light L2 is input to the wavelength monitor 30 as measured light R2.

  The interference output lights C1 to C4 of the wavelength monitor 30 are received by the light receiver 40, converted into sinλ, cosλ, -sinλ, and -cosλ electrical signals and input to the arithmetic circuit 50, and the wavelength measurement signal λi is calculated. It is output to the control circuit 60. The control circuit 60 forms a feedback control system that adjusts the wavelength of the laser light R0 transmitted from the variable wavelength laser light source 10 based on the deviation between the wavelength measurement signal λi and the wavelength target value λs.

  FIG. 3 is a block diagram showing an optical system of a conventional optical wavelength measuring device using a Michelson interferometer. The light to be measured L0 is input to the main beam splitter 2 via the condenser lens 1, and is branched into two by the branch film 21 into the reflected light L1 and the transmitted light L2.

  The reflected light L 1 is reflected by the right-angle prism mirror 3 and returns to the main beam splitter 2. The transmitted light L2 is reflected by the right-angle prism mirror 4, returns to the main beam splitter 2, and is combined with the reflected light L1 by the branch film 21.

  A λ / 8 wavelength plate 5 is inserted in the forward and return paths of the branched light L1, and converts the polarization state of L1 from linearly polarized light to elliptically polarized light. Here, since the λ / 8 wavelength plate 5 is inserted in both the forward path and the return path of the branched light L1, the polarization state changes by λ / 4, that is, 90 degrees when the branched light L1 reciprocates along the optical path.

  A phase compensator 6 is disposed in the forward and return paths of the branched light L2. The phase compensator 6 cancels (compensates) the change in the optical path length of the branched light L1 due to the temperature change by the change in the optical path length of the branched light L2 and the refractive index temperature dependency of the phase compensator 6. For this reason, even if a temperature change occurs, a stable and accurate operation can be performed without causing a significant change in the characteristics of the interferometer.

  In the branch film 21, the branched light L1 whose polarization state has changed by 90 degrees and the branched light L2 whose polarization state has not changed are incident and combined to generate interference light. The interference lights L3 and L4 obtained by this interference are branched at a predetermined intensity ratio (for example, 1: 1), one interference light L3 is incident on the polarization beam splitter 7, and the other interference light L4 is polarized. The light enters the beam splitter 8.

  The interference light L3 incident on the polarization beam splitter 7 is branched according to the polarization state and incident on the light receiving elements 9a and 9b formed of photodiodes. The interference light incident on the polarization beam splitter 8 is branched according to the polarization state and incident on the light receiving elements 10a and 10b formed of photodiodes. The change in wavelength is measured from the light reception results of these light receiving elements 9a, 9b and 10a, 10b.

Japanese Patent Laid-Open No. 2002-202203

  In the temperature compensation according to the conventional method, even if the phase compensator 6 is provided and stabilized with respect to the temperature, the error of the actual element parameter cannot be completely eliminated, so that there is a remaining temperature characteristic.

  In fact, the linearity coefficient of the metal material and the linearity of the refractive index temperature coefficient of a dielectric doubler such as glass are different, so there are restrictions on the applicable range when reducing temperature characteristics, and a wide external There is a limit to temperature compensation in the temperature range.

  For this reason, when this optical wavelength measuring device is the wavelength monitor of the variable wavelength laser light source shown in FIG. 2, there is a limit to the wavelength control accuracy of the output light R1, and a predetermined wavelength accuracy cannot be ensured in a wide external temperature range. There's a problem.

  The present invention has been made to solve the above-described problems, and it is possible to obtain a stable temperature characteristic in a wide external temperature range by utilizing the function of a phase compensator having a refractive index temperature dependency. The purpose is to realize an optical wavelength measuring device.

In order to achieve such a subject, the present invention has the following configuration.
(1) The light to be measured is branched into a first branched light and a second branched light by a main beam splitter, and the first branched light and the second branched light are interfered by the main beam splitter via different optical paths. And a wave plate disposed on at least one of the optical path of the first branched light and the optical path of the second branched light; and at least one of the optical path of the first branched light and the optical path of the second branched light A phase compensator having a refractive index temperature dependence arranged on the optical path, a polarization beam splitter that branches the interference light obtained by the interference according to the polarization state, and interference light branched by the polarization beam splitter. In a light wavelength measuring device comprising a light receiving element for receiving light,
Heating means attached to the phase compensator;
A control circuit for controlling the temperature of the phase compensator via the heating means based on an external temperature;
An optical wavelength measuring device comprising:

(2) A memory in which an operation amount to the heating unit is stored in advance corresponding to the external temperature is provided, and the control circuit refers to the memory when the measured value of the external temperature is acquired. The optical wavelength measuring device according to (1), wherein a predetermined operation amount is output.

(3) The main beam splitter includes a first beam splitter that branches the measured light into a first branched light and a second branched light, and a second beam splitter that overlaps the first and second branched lights again. It is composed of a plurality of homogeneous beam splitters, and the positional relationship between the branch films of the first and second beam splitters and the substrate on which they are formed is arranged to be opposite to each other. The optical wavelength measuring device according to (1) or (2).

According to the configuration of the present invention, the following effects can be expected.
(1) Using an existing phase compensator having a refractive index temperature dependency and controlling the temperature based on the external temperature, the temperature stability of the output of the interferometer as an optical wavelength measuring device is remarkably improved. be able to.

(2) Accordingly, it is possible to improve the temperature stability of the output wavelength of the wavelength tunable laser light source using the optical wavelength measuring device to which the present invention is applied as a wavelength monitor in a wide external temperature range.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment of an optical wavelength measuring device to which the present invention is applied. The same elements as those of the conventional configuration described with reference to FIG.

  The first feature of the present invention compared to the conventional configuration is the heating means 100 attached to the phase compensator 6. The heating means 100 may be a resistor heater such as a nichrome wire or a Peltier element.

  The control circuit 200 outputs an operation amount M such as current to the heating means 100. The control circuit 200 includes a memory 300 in which the operation amount to the heating unit 100 corresponding to the external temperature is stored in advance by a table unit or the like, and refers to the memory 300 when the measured value T is acquired from the external temperature sensor 400. Then, a predetermined operation amount M is output to the heating means 100.

  Although one external temperature sensor 400 is exemplified, a plurality of measurement values T obtained by calculating a plurality of sensor values (average calculation etc.) by arranging a plurality of external temperature sensors in the vicinity of the apparatus can also be used.

  The second feature of the present invention compared to the conventional configuration is the configuration of the main beam splitter 2. That is, the main beam splitter 2 adheres the inclined portions of the right-angle prisms 2a and 2b, which are transparent members, via the optical adhesive layer 500, and uses the adhesive layer as a substrate to make the first branch film 601 and the second branch of the same quality. The film 602 is sandwiched.

  The positional relationship between the first branch film 601 and the second branch film 602 is arranged to be opposite to each other with the substrate interposed therebetween. A first beam splitter is formed by the first branch film 601 and the substrate, and a second beam splitter is formed by the second branch film 602 and the substrate.

  The first beam splitter branches the measured light L0 into the first branched light L1 and the second branched light L2. The second beam splitter again superimposes the first and second branched lights reflected and returned by the right-angle prism.

  With such a main beam splitter configuration, each of the branched lights L1 and L2 passes through the optical adhesive layer 500 once after being branched by the branch film 601 and before entering the branch film 602. For this reason, when a temperature change occurs, it is possible to prevent a situation in which the optical path length of only one of the branched lights L1 and L2 greatly fluctuates as compared with the other optical path length, thereby stably and accurately. Operation can be performed.

  Further, with such a configuration of the main beam splitter, even when a phase difference between the branched lights L1 and L2 occurs when the measured light L0 is branched by the first branch film 601 of the main beam splitter 2, The phase difference is compensated by the branched lights L1 and L2 entering the second branched film 602 of the beam splitter 2, and the phenomenon (PDFS) in which the phase of the extended interferometer changes depending on the polarization state of the light to be measured L0 is also reduced. .

It is a functional block diagram which shows one Embodiment of the optical wavelength measuring apparatus to which this invention is applied. It is a functional block diagram of a wavelength tunable laser light source using an optical wavelength measuring device using an interferometer as a wavelength monitor. It is a block diagram which shows the optical system of the conventional optical wavelength measuring apparatus by a Michelson type interferometer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Condensing lens 2 Main beam splitter 3, 4 Right angle prism mirror 5 (lambda) / 8 wavelength plate 6 Phase compensator 7, 8 Deflection beam splitter 8a, 8b Light receiving element 9a, 9b Light receiving element 100 Heating means 200 Control circuit 300 Memory 400 External Temperature sensor 500 Optical adhesive layer 601 602 Branched film

Claims (3)

The light to be measured is branched into a first branched light and a second branched light by a main beam splitter, and the first branched light and the second branched light through different optical paths are caused to interfere with each other by the main beam splitter, A wave plate disposed on at least one of the optical path of the first branched light and the optical path of the second branched light; and on at least one optical path of the optical path of the first branched light and the optical path of the second branched light. A phase compensator having a refractive index temperature dependency, a polarization beam splitter that branches the interference light obtained by the interference according to the polarization state, and a light receiving device that receives the interference light branched by the polarization beam splitter. In an optical wavelength measuring device comprising an element,
Heating means attached to the phase compensator;
A control circuit for controlling the temperature of the phase compensator via the heating means based on an external temperature;
An optical wavelength measuring device comprising:   A memory that pre-stores an operation amount to the heating unit corresponding to the external temperature is provided, and the control circuit refers to the memory when the measured value of the external temperature is acquired, and performs a predetermined operation on the heating unit. The optical wavelength measuring device according to claim 1, wherein the optical wavelength measuring device outputs a quantity.   The main beam splitter includes two homogeneous beams: a first beam splitter that branches the measured light into a first branched light and a second branched light, and a second beam splitter that superimposes the first and second branched lights again. 2. A beam splitter, wherein the first and second beam splitters are arranged so that the positional relationship between each branch film and the substrate on which they are formed is opposite to each other. 3. The optical wavelength measuring device according to 1 or 2.

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