JP2011065026A - Fiber bragg grating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an FBG (Fiber Bragg Grating) device that accurately suppresses operating wavelength fluctuation of an FBG and has a simple structure. <P>SOLUTION: This FBG device has: an optical fiber device having the FBG; a casing that has a through hole passing the optical fiber device and is made of an invar alloy; a fixing section for filling the through hole and fixing the optical fiber device to the casing; a thermo-module having a heat control element and arranged inside the casing; a mounting plate having a temperature sensor and arranged on the thermo-module; and a holding section for holding the FBG so that it moves in the extension direction of the FBG on the surface of the mounting plate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fiber Bragg grating (FBG) device used as an encoder and a decoder in optical code division multiplexing transmission.

  In recent years, in response to a rapid increase in communication demand due to the spread of the Internet, high-speed and large-capacity networks using optical fibers are being developed. In such a high-speed and large-capacity network, an optical multiplex transmission technology that transmits optical pulse signals for a plurality of communication channels in a single optical fiber transmission line is indispensable.

  In the optical multiplex transmission technology, research has been conducted on optical time division multiplexing (OTDM), wavelength division multiplexing (WDM), and optical code division multiplexing (OCDM). Yes. The OCDM has a feature in which a plurality of communication channels can be set in the same time slot on the time axis, and a plurality of communication channels can be set in the same wavelength on the wavelength axis. Research is underway.

  In OCDM, modulation is performed with a code different for each channel on the transmission side, and demultiplexing is performed by decoding with the same code as that on the transmission side on the reception side. That is, in the OCDM, when decoding on the receiving side, it is necessary to use the same code as that used for encoding on the transmitting side. Therefore, if the code used for encoding is not known, decoding is performed. In other words, information security can be ensured with high accuracy.

  As an encoding means in the OCDM, a wavelength hop / time spread combination method (hereinafter simply referred to as a wavelength hop method) and a binary phase code that code a plurality of wavelengths and an arrangement order of each wavelength on the time axis are used. A phase code method is known.

  In the phase code type OCDM, an optical pulse signal is spread on the time axis according to a certain rule (that is, a code set in the encoder) by an encoder, so that an optical pulse train (hereinafter also referred to as a chip pulse train). Is formed. The chip pulse train is decoded into an original optical pulse signal by a decoder. At this time, the relative phase difference between each chip pulse of the chip pulse train formed by the encoder becomes a code. That is, the encoder gives a relative phase difference between the chip pulses when the optical pulse signal is diffused into the chip pulse train, and the decoder cancels the relative phase difference between the chip pulses.

  When the code on the transmitter encoder and the receiver decoder are the same, the correlation waveform (autocorrelation waveform) reproduced by the decoder cancels the relative phase difference between the chip pulses given by the encoder. Therefore, the waveform has a strong peak. On the other hand, when the codes on the transmitting side encoder and the receiving side decoder are different, the correlation waveform (cross correlation waveform) reproduced by the decoder has a relative phase difference between chip pulses given by the encoder. Since it is not canceled, the waveform has a plurality of small peaks.

  As an encoder / decoder for an OCDM transmission system, one using a fiber Bragg grating (FBG) has been conventionally known. The FBG is a device in which a lattice-like refractive index change region (grating) is formed in the core of an optical fiber, and has a feature of reflecting light of a specific wavelength. In recent years, attention has been paid to a technique using an SSFBG (Superstructured FBG) having a multipoint phase shift structure for an encoder / decoder of an OCDM. In such an SSFBG, a plurality of identically configured FBGs (hereinafter referred to as unit FBGs) are formed in the same optical fiber so that the interval between adjacent unit FBGs is “0” or any Set to interval.

  Since the FBG is an optical fiber type device, the insertion loss with respect to the optical network using the optical fiber is small, the alignment work is not required when connecting, a planar optical circuit (PLC: Planar Lightwave Circuit) or Compared with a device configured with an arrayed waveguide grating (AWG), it has advantages such as high affinity to an optical network.

  The Bragg reflection wavelength of the FBG (hereinafter also referred to as the operating wavelength) varies depending on the strain applied to the FBG or the temperature of the FBG. In particular, in the transmission by the phase code type OCDM, when the operating wavelength of the FBG constituting the transmitting side encoder and the operating wavelength of the FBG constituting the receiving side decoder differ by several pm or more, decoding is performed on the receiving side. Unable to execute. That is, in order to perform decoding with high accuracy, the encoder and the FBG that configure the transmitting side encoder and the FBG that configures the receiving side decoder have a difference in operating wavelength of less than several pm. It is necessary to stabilize the operating wavelength of the FBG constituting the decoder or to adjust the operating wavelength of at least one of the FBGs constituting the encoder or decoder as needed.

  As a means for stabilizing the operating wavelength of the FBG with respect to the environmental temperature change, for example, by fixing the FBG to a substrate having a negative thermal expansion coefficient, the FBG wavelength fluctuation amount accompanying the environmental temperature change is used as a basis. There is a method of compensating by the amount of FBG wavelength variation caused by the stress varied by thermal expansion and contraction of the material (that is, a method using a non-thermosensitive optical element) (Patent Document 1). In addition, a method for compensating for the wavelength fluctuation amount of the FBG accompanying the change in the environmental temperature by the wavelength fluctuation amount of the FBG accompanying the stress by forming the cantilever with two or more kinds of metals having different thermal expansion coefficients (that is, temperature compensated optical) (Patent Document 2). Further, as a means for adjusting the operating wavelength of the FBG, there is a method of controlling the temperature of the FBG to be constant without depending on the environmental temperature using a thermo module including a Peltier element (Patent Document 3).

Special table 2000-503415 Special table 2003-526812 JP 2005-173246 A

  However, all of the FBG wavelength fluctuation countermeasures described above are methods against environmental temperature changes, and thus are not effective for distortions directly applied to the FBG, and the FBG wavelength fluctuation countermeasures are not sufficient. That is, if not only the environmental temperature change but also the tension applied to the FBG from the outside is not dealt with, the wavelength fluctuation of the FBG cannot be sufficiently suppressed.

  Further, with the rapid increase in communication demand in recent years, there is a demand for cost reduction of each communication device. Use of Patent Document 2) makes it difficult to meet such demands.

  An object of the present invention has been made in view of the above circumstances, and an object of the present invention is to provide an FBG device that can suppress fluctuations in the operating wavelength of the FBG with high accuracy and has a simple structure.

  In order to solve the above-described problems, an FBG device according to the present invention includes an optical fiber device including a fiber Bragg grating, a casing including a through hole through which the optical fiber device passes and made of an invar alloy, filling the through hole, and optically. A fixing part for fixing the fiber device to the casing, a thermo module provided with a thermal control element and disposed inside the casing, a mounting plate provided with a temperature sensor and disposed on the thermo module, and a fiber Bragg grating And a holding part for holding the fiber Bragg grating so as to be movable in the extending direction on the surface of the mounting plate.

  The FBG device of the present invention can suppress fluctuations in the operating wavelength of the FBG with high accuracy even when tension is applied from the outside due to the structure described above and when the temperature of the installation environment of the FBG device changes. . Moreover, since the FBG apparatus of the present invention does not require a special material and is configured with a simple structure, the cost required for design and manufacture can be reduced.

It is a block block diagram of an OCDM transmission apparatus. It is a perspective view of the FBG apparatus in Example 1 of this invention. (A) is an XY cross-sectional view of the FBG device in FIG. 2, (b) is a YZ cross-sectional view of the FBG device in FIG. 2, and (c) is in FIGS. 3 (a) and 3 (b). It is sectional drawing in line 3c-3c. It is a simulation result of the wavelength fluctuation accompanying the change of the applied tension from the outside of the FBG apparatus in Example 1 of this invention. It is a simulation result of the wavelength fluctuation accompanying the environmental temperature change of the FBG apparatus in Example 1 of this invention. (A) is XY sectional drawing of the FBG apparatus in Example 2, (b) is YZ sectional drawing of the FBG apparatus in Example 2, (c) is FIG. 6 (a), (b). ) Is a cross-sectional view taken along line 6c-6c. It is a simulation result of the wavelength fluctuation accompanying the change of the applied tension from the outside of the FBG apparatus in Example 2 of the present invention. It is a simulation result of the wavelength fluctuation accompanying the environmental temperature change of the FBG apparatus in Example 2 of this invention. 6 is an XZ sectional view of an FBG device in Example 3. FIG. 10 is an XZ sectional view of an FBG device in Example 4. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  First, a configuration of an optical code division multiplexing (OCDM) transmission apparatus including a fiber Bragg grating (FBG) apparatus of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an OCDM transmission apparatus.

  The OCDM transmission apparatus 10 includes a transmission unit 20 and a reception unit 40, and the transmission unit 20 and the reception unit 40 are connected by a transmission path 60. The signal transmitted by the OCDM transmission apparatus 10 is an optical pulse signal, and the optical pulse signal is a binary digital electric pulse signal carrying information to be transmitted (this signal is a binary digital signal of “0” or “1”). This is a pulse signal whose value is reflected in the voltage level).

  The transmitter 20 includes an optical pulse train generator 21, a modulation signal generator 22, an optical modulator 23, a first optical circulator 24, a first fiber Bragg grating (FBG) device 25 that is an encoder, and a temperature. The controller 26 is configured. The optical pulse train generator 21 generates an optical pulse train 31. The modulation signal generator 22 supplies information to be transmitted to the optical modulator 23 as a binary digital electric pulse signal 32.

  The optical pulse signal 33 to be transmitted output from the optical modulator 23 is incident on the first FBG device 25 via the first optical circulator 24. The encoded optical pulse signal is supplied from the first FBG device 25 to the first optical circulator 24 again. The encoded optical pulse signal is transmitted to the transmission line 60 as the optical pulse signal 34 through the first optical circulator 24, propagates through the transmission line 60, and is supplied to the receiving unit 40.

  The first FBG device 25 is provided with a temperature sensor (not shown) which will be described later, the temperature of the FBG constituting the first FBG device 25 is constantly measured, and the result is sent to the temperature controller 26 as a temperature signal. 35 is supplied. In response to the supplied temperature signal 35, the temperature controller 26 supplies the first FBG device 25 with a drive signal 36 for driving a thermo module, which will be described later, and performs temperature control.

  The receiving unit 40 includes a second optical circulator 41, a second FBG device 42 that is a decoder, an optical coupler 43, a photoelectric converter 44, a wavelength monitor 45, a wavelength control unit 46, and a temperature controller 47. The photoelectric converter 44 converts the optical pulse signal into an electric pulse signal. The wavelength monitor 45 measures the degree of autocorrelation (eye opening size) of the optical pulse signal 51 supplied from the optical coupler 43. The wavelength controller 46 receives the output 52 from the wavelength monitor 45 and supplies a temperature control signal 53 to the temperature controller 47. In response to the temperature control signal 53, the temperature controller 47 supplies the second FBG device 42 with a drive signal 54 for driving a thermo module, which will be described later, and controls the temperature.

  The optical pulse signal 55 transmitted through the transmission path 60 is incident on the second FBG device 42 via the second optical circulator 41 and decoded. The decoded optical pulse signal is supplied to the second optical circulator 41 again. Further, the decoded optical pulse signal enters the optical coupler 43 via the second optical circulator 41 and is demultiplexed into the optical pulse signal 56 and the optical pulse signal 51. The optical pulse signal 56 is restored as an electric pulse signal 57 by the photoelectric converter 44. That is, the binary digital electric pulse signal 32 that is information to be transmitted is restored as the binary digital electric pulse signal 57 by the receiving unit 40.

  The second FBG device 42 is provided with a temperature sensor (not shown) to be described later, and the temperature of the FBG constituting the second FBG device 42 is constantly measured, and the result is sent to the temperature controller 47 as a temperature signal. 58. In addition to the drive signal 54 corresponding to the temperature control signal 53, the temperature controller 47 supplies the drive signal 54 in order to make the temperature of the FBG constant according to the supplied temperature signal 58.

  Next, the structure of the FBG apparatus according to the present invention will be described in detail with reference to FIGS. 2 and 3A, 3B, and 3C. Since the first FBG device 25 of the transmission unit 20 and the second FBG device 42 of the reception unit 40 described above have the same configuration, the second FBG device 42 is represented below for convenience of explanation. I will explain.

  FIG. 2 is a schematic perspective view of the FBG device. In the following, the horizontal direction in FIG. 2 is defined as the X-axis direction, the vertical direction in the drawing is defined as the Z-axis direction, and the direction along the extending direction of the FBG device is defined as the Y-axis direction. 3A is an XY cross-sectional view of the central portion of the FBG device, FIG. 3B is a YZ cross-sectional view of the central portion of the FBG device, and FIG. 3C is a cross-sectional view of FIG. ), (B) is a cross-sectional view taken along line 3c-3c (shown by a broken line).

  As shown in FIGS. 2, 3 (a), and 3 (b), the second FBG device 42 includes an optical fiber device 71, a mounting plate 72, a thermo module 73, a temperature sensor 74, and a casing 75. ing.

  A thermo module 73 is disposed on the inner bottom surface of the casing 75. Further, a mounting plate 72 is disposed on the thermo module 73. On the surface of the mounting plate 72 (that is, the surface opposite to the contact surface with the thermo module 73), a groove 72a for placing the optical fiber device 71 is formed. Specifically, as shown in FIG. 3C, a groove 72a having a V-shaped cross section is formed along the longitudinal direction (Y-axis direction).

  In the optical fiber device 71, an FBG operating as a phase encoder is formed in the core of the optical fiber. The optical fiber device 71 is placed on the groove 72 a so that the region where the FBG is formed (FBG formation region 71 a) is located at the center of the mounting plate 72. Furthermore, the optical fiber device 71 is fixed in the holding regions 72b at both ends of the mounting plate 72 so that the contact with the mounting plate 72 is held by the adhesive holding material 76 (first adhesive). More specifically, as shown in FIG. 3C, the adhesive holding member 76 covers the optical fiber device 71 and fills the groove 72a in the holding region 72b. Here, the adhesive holding member 76 has a weak adhesive force with respect to the coating material of the optical fiber device 71 and merely suppresses the movement of the optical fiber device 71 in the X-axis direction and the Z-axis direction. That is, the optical fiber device 71 is slidably surrounded by the adhesive holding member 76. Thereby, when a tension is applied in the longitudinal direction (Y-axis direction) of the optical fiber device 71, the optical fiber device 71 can move so as to slide on the groove of the mounting plate 72. More specifically, for example, in a state where the optical fiber device 71 is not fixed to a casing 75 described later, when one end of the optical fiber device 71 is pulled, the optical fiber device 71 is attached to the mounting plate 72. The optical fiber device 71 slides out of the casing 75 in the Y-axis direction on the groove 72a. The adhesive holding member 76 has a strong adhesive force to the mounting plate 72 and is fixed to the mounting plate 72.

  Since an acrylic coating resin is generally used as the coating material for the optical fiber device 71, for example, PARQIT EXGT-3003-1 manufactured by Otex Co., Ltd. can be used as the adhesive holding material 76.

  A through hole 75 a is provided in the casing 75, and the optical fiber device 71 is drawn out of the casing 75 through the through hole 75 a. The through hole 75a is disposed at a position where the optical fiber device 71 mounted on the mounting plate 72 can be pulled out to the outside without being bent or bent. That is, the through hole 75a is disposed at a position along the Y-axis direction from the groove 72a in the X-axis direction, and is disposed at the same position as the groove 72a in the Z-axis direction.

  In the through hole 75a, a gap between the optical fiber device 71 and the casing 75 is filled with an adhesive fixing material 77 (second adhesive). Thereby, the optical fiber device 71 is fixed to the casing 75 and the casing 75 is sealed. Here, the adhesive fixing material 77 covers the optical fiber device 71 and fixes the optical fiber device 71 from the casing 75 so as not to move. That is, the adhesive fixing material 77 is different from the adhesive holding material 76 in that the adhesive force is strong with respect to the coating material of the optical fiber device 71, and the optical fiber device 71 moves in the X axis direction, the Y axis direction, and the Z axis direction. Suppressed. Thereby, even if tension is applied to the optical fiber device 71 from the outside of the casing 75, the FBG located inside the casing 75 is not affected by the tension. In the present embodiment, the adhesive fixing material 77 serves as a fixing portion.

For example, as the adhesive fixing material 77, it is desirable to use an epoxy adhesive having a Young's modulus after curing of about 100 GPa or more and a glass transition temperature (T _g ) of about 80 degrees Celsius (80 ° C.) or more. In addition to the epoxy adhesive described above, for example, an acrylic adhesive having a Young's modulus of about 10 GPa or less and a glass transition temperature (T _g ) of about 40 ° C. or more can be used. The effect obtained is limited. Further, the adhesive holding material 76 may be either a photo-curing resin or a thermosetting resin.

  The mounting plate 72 is preferably made of a metal material having a high thermal conductivity such as copper or aluminum. This is because the heating and cooling in the thermo module 73 are efficiently transmitted to the optical fiber device 71, and the temperature of the optical fiber device 71 is changed to a predetermined temperature in a short time. Further, the mounting plate 72 is not limited to the metal described above, and may be made of an alloy (that is, Invar) having a low coefficient of thermal expansion near normal temperature. In such a case, it is preferable that the temperature difference between the optical fiber device 71 and the mounting plate 72 is less than about 1 ° C. at least in the FBG formation region 71b.

  The thermo module 73 is a heating / cooling module using a Peltier element that is a thermal control element. That is, heating and cooling can be performed freely only by changing the direction of the current supplied to the Peltier element. In the present embodiment, only one thermo module 73 is arranged. However, a structure in which a plurality of thermo modules 73 are arranged in consideration of the shape and dimensions of the mounting plate 72 and the dimensions of the FBG formation region 71a may be employed. .

  The temperature sensor 74 is composed of a thermistor. The temperature sensor 74 is embedded in the mounting plate 72. The temperature sensor 74 is not limited to the above contents, and may be composed of, for example, a thermocouple or a platinum thermal resistor, and may be fixed to the upper surface or side surface of the mounting plate 72.

  The casing 75 is provided with a terminal portion (not shown). The terminal portion includes a pair of power supply terminals to the thermo module 73 and a pair of output terminals of the temperature sensor 74. A power supply terminal to the thermo module 73 and an output terminal of the temperature sensor 74 are connected to the temperature controller 47 (see FIG. 1). Thereby, heating / cooling of the thermo module 73 is controlled according to the temperature of the mounting plate 72 detected by the temperature sensor 74, and the temperature of the FBG mounted on the mounting plate 72 can be maintained at a desired temperature. it can.

The casing 75 is made of an alloy having a very small coefficient of thermal expansion near normal temperature (for example, a super invar having an invar alloy having a thermal expansion coefficient of about 1 × 10 ⁻⁸ / K). The invar alloy is, for example, invar having a thermal expansion coefficient of about 1 × 10 ⁻⁶ / K or super invar having a thermal expansion coefficient of about 1 × 10 ⁻⁸ / K. Without limitation, the Invar alloy is an alloy having a wide range of properties.

  Further, for example, the casing 75 may be configured by a removable lid and a half to which the lid is attached. After the optical fiber device 71 is mounted inside the casing 75 (that is, inside the half) (that is, after the optical fiber device 71 is held by the adhesive holding material 76 and fixed by the adhesive fixing material), the lid portion May be closed.

  Next, various wavelength control operations in the FBG device according to the first embodiment of the present invention described above will be described.

  First, the case where the thermo module 73 is driven according to the drive signal supplied from the temperature controller 47 will be described. When a drive signal is supplied from the temperature controller 47 to the thermo module 73, the thermo module 73 is driven and heating or cooling processing is started. The temperature of the mounting plate 72 changes due to the heating or cooling process. Furthermore, since the mounting plate 72 is made of a metal material having a high thermal conductivity, the temperature of the FBG formation region 71a also changes so as to follow the temperature change of the mounting plate 72. As a result, the temperature of the FBG is maintained at a predetermined temperature.

  At this time, the mounting plate 72 expands and contracts according to a temperature change caused by heating or cooling processing. However, the optical fiber device 71 is held in the holding regions 72b at both ends of the mounting plate 72 so that the optical fiber device 71 can slide on the groove of the mounting plate 72 when tension is applied in the longitudinal direction (Y-axis direction). Therefore, even when the mounting plate 72 expands and contracts, the tension related to the expansion and contraction is not transmitted to the FBG. That is, even when the FBG temperature adjustment process is performed, the operating wavelength of the FBG depends only on the temperature change of the FBG. Thereby, it is not necessary to consider the expansion and contraction of the mounting plate 72 accompanying the temperature change, and the required wavelength fluctuation amount can be easily controlled only by the temperature adjustment.

  Secondly, a case where a tension is applied to the second FBG device 42 from the outside will be described. When the optical fiber device 71 pulled out from the casing 75 is pulled, a tension is applied to the optical fiber device 71, and the tension is transmitted to a portion where the optical fiber device 71 is fixed to the casing 75 by the adhesive fixing material 77. . However, since the Young's modulus of the adhesive fixing material 77 is as large as 100 GPa or more and the movement of the optical fiber device 71 in the X-axis direction, the Y-axis direction, and the Z-axis direction is suppressed by the adhesive fixing material 77, the applied tension Is not transmitted to the FBG formation region 71 a inside the casing 75. That is, even if tension is applied from the outside of the casing 75, the FBG inside the casing 75 is not affected. This will be described with reference to FIG.

  FIG. 4 shows a simulation result of the wavelength fluctuation of the FBG due to the tension applied to the optical fiber device 71 from the outside of the casing 75 in the FBG apparatus of the present embodiment. The horizontal axis in FIG. 4 is the tension (N) applied from the outside of the casing 75, and the vertical axis is the FBG wavelength variation (pm). As shown in FIG. 4, as the tension applied to the optical fiber device 71 increases, the wavelength fluctuation amount of the FBG also increases. However, even when the applied tension is 10 N, the wavelength fluctuation amount of the FBG is about 2 pm, so the influence on the encoding / decoding characteristics is small. If the fluctuation is about 2 pm, the fluctuation is easily corrected by readjusting the control temperature of the FBG (that is, the drive signal 54 is supplied again from the temperature controller 47 in response to the temperature control signal 53). can do.

Further, since the glass transition temperature (T _g ) of the adhesive fixing material 77 is about 80 ° C. or higher, the adhesive fixing material 77 is softened even when the environmental temperature becomes high, and the tension transmission control ability deteriorates. Nor.

  Third, the case where the temperature of the environment where the FBG apparatus of the present embodiment is installed changes will be described.

When the temperature of the environment where the second FBG device 42 is installed changes, the casing 75 expands and contracts in the X-axis, Y-axis, and Z-axis directions. Furthermore, since the optical fiber device 71 is fixed to the casing 75 by the adhesive fixing material 77, the expansion and contraction of the casing 75 is transmitted to the FBG formation region 71 a located inside the casing 75. However, since the thermal expansion coefficient of the casing 75 is about 1 × 10 ⁻⁸ / K or less in the second FBG device 42 of the present embodiment, the expansion / contraction amount of the casing 75 due to the environmental temperature change is small, and the control wavelength of the FBG Will not be affected. This will be described with reference to FIG.

  FIG. 5 shows a simulation result of the FBG wavelength variation when the temperature of the environment in which the FBG device is installed changes in the FBG device of the present embodiment. The horizontal axis in FIG. 5 is the temperature (° C.) of the environment where the second FBG device 42 is installed, and the vertical axis is the FBG wavelength variation (pm). The reference is set when the environmental temperature is 20 ° C. (that is, the FBG wavelength fluctuation amount is “0”). As shown in FIG. 5, as the environmental temperature rises from −40 ° C., the wavelength fluctuation amount of the FBG gradually decreases. This is because, as described above, the casing 75 expands and contracts with the environmental temperature change, and the expansion and contraction is transmitted to the FBG formation region 71a. However, even when the environmental temperature changes from −40 ° C. to + 80 ° C., the wavelength fluctuation of the FBG due to the expansion and contraction of the casing 75 is about −7 pm to +5 pm (12 pm in width). With such a wavelength fluctuation, the fluctuation can be easily corrected by readjusting the control temperature of the FBG.

Since the thermo module 73 is composed of Peltier elements, the casing 75 is cooled when the mounting plate 72 is heated, or the casing 75 is heated when the mounting plate 72 is cooled. However, since the thermal expansion coefficient of the casing 75 is about 1 × 10 ⁻⁸ / K or less, the amount of elongation due to the heating or cooling is small, and the control wavelength of the FBG is not affected.

  As described above, the FBG device of the present invention includes an optical fiber device having a fiber Bragg grating, a casing made of an invar alloy with a through-hole through which the optical fiber device passes, and a casing filled with the through-hole and filled with the optical fiber device. A fixing part for fixing to the surface, a thermo module including a Peltier element and disposed inside the casing, a mounting plate provided with a temperature sensor and disposed on the thermo module, and a fiber Bragg grating on the surface of the mounting plate And a holding portion that holds the fiber Bragg grating so as to be movable in the extending direction.

  The FBG device of the present invention can suppress fluctuations in the operating wavelength of the FBG with high accuracy even when tension is applied from the outside due to the structure described above and when the temperature of the installation environment of the FBG device changes. . Moreover, since the FBG apparatus of the present invention does not require a special material and is configured with a simple structure, the cost required for design and manufacture can be reduced.

  In this embodiment, the optical phase encoder in OCDM has been described as an example. However, the present invention is not limited to this. For example, the present invention is applied to a wavelength filter device in wavelength division multiplexing (WDM). You can also.

  The FBG apparatus according to the second embodiment of the present invention will be described in detail with reference to FIGS. 6 (a), (b), and (c). The FBG device according to the second embodiment is substantially the same as the FBG device according to the first embodiment, but only the structure of a part for drawing out the optical fiber device from the casing is different. In the following, the same structural parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  Each drawing in FIG. 6 is the same as each drawing in FIG. 3, FIG. 6 (a) is an XY sectional view in the central portion of the FBG device, and FIG. 6 (b) is a YZ in the central portion of the FBG device. FIG. 6C is a cross-sectional view taken along line 6c-6c (shown by a broken line) in FIGS. 6A and 6B.

  As shown in FIGS. 6A and 6B, the third FBG device 80 is similar to the second FBG device 42 in that the optical fiber device 71, the mounting plate 72, the thermo module 73, and the temperature sensor. 74 and a casing 81. The optical fiber device 71 is drawn out of the casing 75 through a through tube 82 fixed to the through hole 81 a of the casing 81. The optical fiber device 71 is fixed to the through tube 82 at both ends of the through tube 82 by an adhesive fixing material 83 (second adhesive body).

  The adhesive fixing material 83 covers the optical fiber device 71 and fixes the optical fiber device 71 so as not to move from the through tube 82. That is, the adhesive fixing material 83 has a strong adhesive force with respect to the coating material of the optical fiber device 71 and suppresses movement of the optical fiber device 71 in the X-axis direction, the Y-axis direction, and the Z-axis direction. Thereby, even if tension is applied to the optical fiber device 71 from the outside of the casing 81, the FBG located inside the casing 81 is not affected by the tension. In the present embodiment, a fixing portion is formed from the through tube 82 and the adhesive fixing material 83.

For example, the adhesive fixing material 83 has a Young's modulus after curing of about 100 GPa or more and a glass transition temperature (T _g ) of about 80 degrees Celsius (80 ° C.) or more, like the adhesive fixing material 77 of Example 1. It is desirable to use some epoxy adhesive. In addition to the epoxy adhesive described above, for example, an acrylic adhesive having a Young's modulus of several GPa and a glass transition temperature (T _g ) of about 40 ° C. or more can be used. The effect is limited.

  Hereinafter, the adhesive fixing material positioned inside the casing 81 is also referred to as an adhesive fixing material 83a, and the adhesive fixing material positioned outside the casing 81 is also referred to as an adhesive fixing material 83b.

Unlike the case of the first embodiment, the casing 81 is made of an alloy having a thermal expansion coefficient of about 2 × 10 ⁻⁶ / K or less. The through tube 82 is preferably made of a metal such as aluminum or copper, but may be made of other metal materials as long as the coefficient of thermal expansion is larger than that of the casing material.

  Next, various wavelength control operations in the FBG device according to the second embodiment of the present invention described above will be described.

  First, the FBG wavelength control operation in the case where the thermo module 73 is driven in accordance with the drive signal supplied from the temperature controller 47 is the same as that in the first embodiment, and thus the description thereof is omitted. This is because the structural members of the FBG device when the thermo module 73 is driven according to the drive signal have the same structure in the first and second embodiments. Specifically, the optical fiber device 71 is held by the adhesive holding member 76.

  Further, the FBG wavelength control operation in the case where a tension is applied to the third FBG device 80 from the outside is also the same as that in the first embodiment, and thus the description thereof is omitted. This is because the optical fiber cable 71 is fixed to the through tube 82 in a state where movement in each axial direction is suppressed by the adhesive fixing material 83. FIG. 7 shows the simulation result of the wavelength fluctuation of the FBG due to the tension applied to the optical fiber device 71 from the outside of the casing 75 in the FBG apparatus of the present embodiment. 7 and 4 show that the simulation results are the same, and the third FBG device 80 in the present embodiment also operates with high accuracy with respect to external tension, as in the first embodiment. It can be seen that control is being performed.

  Next, the case where the temperature of the environment where the FBG apparatus of a present Example is installed changes is demonstrated. In the following, a case where the environmental temperature rises will be described as an example in order to simplify the description.

  When the temperature of the environment in which the third FBG device 80 is installed rises, the casing 81 extends. Furthermore, since the optical fiber device 71 is fixed to the casing 81 by the adhesive fixing material 83 and the through tube 82, the extension of the casing 81 is transmitted to the FBG formation region 71a located inside the casing 81. That is, tension is applied to the FBG located inside the casing 81 in the -Y direction.

  Further, when the temperature of the environment in which the third FBG device 80 is installed rises, the through tube 82 also extends. Here, since the optical fiber device 71 is fixed by the adhesive fixing material 83 at both ends of the through tube 82, when the through tube 82 is extended, the FBG located inside the casing 81 rather than the adhesive fixing material 83a has + Y. Tension is applied in the direction. On the contrary, tension is applied in the −Y direction to the optical fiber device 71 drawn out of the casing 81 from the adhesive fixing material 83b.

  From the above, for the FBG located inside the casing 81, the tension due to the extension of the casing 81 and the tension due to the extension of the through tube 82 are applied in opposite directions, so the tension due to the extension of the casing 81 is applied to the through tube 82. Can be offset by the tension of

  In the above description, the case where the environmental temperature increases has been described. However, when the environmental temperature decreases, the casing 81 and the through tube 82 contract, and the direction of tension applied to the optical fiber device 71 is reversed. is there.

  FIG. 8 shows a simulation result of wavelength fluctuation of the FBG when the temperature of the environment in which the FBG apparatus is installed changes in the FBG apparatus of the present embodiment. The horizontal axis in FIG. 8 is the temperature (° C.) of the environment where the third FBG device 80 is installed, and the vertical axis is the FBG wavelength variation (pm). The reference is set when the environmental temperature is 20 ° C. (that is, the FBG wavelength fluctuation amount is “0”). As shown in FIG. 8, the environmental temperature rises from −40 ° C., and the wavelength fluctuation amount of the FBG gradually decreases. This is because, as described above, the casing 81 expands and contracts with the environmental temperature change, and the expansion and contraction is transmitted to the FBG formation region 71a. However, even when the environmental temperature changes from −40 ° C. to + 80 ° C., the wavelength fluctuation of the FBG due to the expansion and contraction of the casing 81 is about −2 pm to +2 pm (4 pm in width). Here, the FBG wavelength fluctuation is smaller than the simulation result shown in FIG. As described above, the expansion and contraction of the through tube 82 occurs in addition to the expansion and contraction of the casing 81, and for the FBG located inside the casing 81, the tension due to the extension of the casing 81 and the tension due to the extension of the through tube 82. Since the tension due to the extension of the casing 81 is offset by the tension due to the extension of the through tube 82 by adding in the opposite directions, it is considered that the wavelength fluctuation of the FBG is smaller than the result of the first embodiment. In addition, if the wavelength fluctuation is such a degree, the fluctuation can be easily corrected by readjusting the control temperature of the FBG.

  As described above, in this embodiment, the wavelength fluctuation of the FBG due to the environmental temperature change can be further reduced, so that it is possible to use a casing material having a larger thermal expansion coefficient than that of the first embodiment.

  The XZ cross section of the groove 72a formed on the surface of the mounting plate 72 in the first embodiment is not limited to the V shape. For example, as shown in FIG. 9, the XZ cross section of the groove 91 may be rectangular.

  Even in such a case, the adhesive holding member 76 has a weak adhesive force with respect to the coating material of the optical fiber device 71 and simply suppresses movement of the optical fiber device 71 in the X-axis direction and the Z-axis direction. Therefore, when a tension is applied in the longitudinal direction (Y-axis direction) of the optical fiber device 71, the optical fiber device 71 can move so as to slide on the groove of the mounting plate 72. Therefore, as in the first and second embodiments, even when the FBG temperature adjustment process is performed, the operating wavelength of the FBG depends only on the temperature change of the FBG. Thereby, it is not necessary to consider the expansion and contraction of the mounting plate 72 accompanying the temperature change, and the required wavelength fluctuation amount can be easily controlled only by the temperature adjustment.

  Further, as in the first embodiment, the depth of the groove 72a is larger than the diameter of the optical fiber device 71, and the optical fiber device 71 is not limited to being disposed in the groove 72a. For example, as shown in FIG. 10, the depth of the groove 101 may be smaller than the diameter of the optical fiber device 71, and the optical fiber device 71 may be exposed from the groove 101. In this case, the adhesive holding member 76 may be provided so as to cover the exposed surface of the optical fiber device 71 and a part of the mounting plate 72 without filling the groove 101.

  Even in such a case, the adhesive holding member 76 has a weak adhesive force with respect to the coating material of the optical fiber device 71 and simply suppresses movement of the optical fiber device 71 in the X-axis direction and the Z-axis direction. Therefore, when a tension is applied in the longitudinal direction (Y-axis direction) of the optical fiber device 71, the optical fiber device 71 can move so as to slide on the groove of the mounting plate 72. Therefore, as in the first and second embodiments, even when the FBG temperature adjustment process is performed, the operating wavelength of the FBG depends only on the temperature change of the FBG. Thereby, it is not necessary to consider the expansion and contraction of the mounting plate 72 accompanying the temperature change, and the required wavelength fluctuation amount can be easily controlled only by the temperature adjustment.

DESCRIPTION OF SYMBOLS 10 OCDM transmission apparatus 20 Transmission part 25 1st FBG apparatus 40 Reception part 42 2nd FBG apparatus 60 Transmission path 71 Optical fiber device 72 Mounting plate 73 Thermo module 74 Temperature sensor 75 Casing 76 Adhesive holding material 77 Adhesive fixing material

Claims (8)

An optical fiber device comprising a fiber Bragg grating;
A casing comprising a through hole for passing the optical fiber device and made of an Invar alloy;
A fixing portion that fills the through hole and fixes the optical fiber device to the casing;
A thermo module comprising a thermal control element and disposed inside the casing;
A mounting plate provided with a temperature sensor and disposed on the thermo module;
A fiber Bragg grating device comprising: a holding portion that holds the fiber Bragg grating so as to be movable in the extending direction of the fiber Bragg grating on the surface of the mounting plate.   2. The fiber Bragg grating device according to claim 1, wherein the holding portion includes a curable first adhesive body that slidably surrounds the fiber Bragg grating and is fixed to the mounting plate.   3. The fiber Bragg grating device according to claim 1, wherein the fixing portion includes a curable second adhesive body that fixes the optical fiber device to the casing. The fiber Bragg grating device according to claim 3, wherein the casing has a thermal expansion coefficient of 1 × 10 ⁻⁸ / K or less.   The said fixing | fixed part consists of a sclerosing | hardenable 2nd adhesive body which fixes the said optical fiber device by the both ends of the through tube fixed to the said through hole, and the said through tube. Fiber Bragg grating device. The fiber Bragg grating device according to claim 5, wherein the casing has a thermal expansion coefficient of 2 × 10 ⁻⁶ / K or less.   The fiber Bragg grating device according to claim 6, wherein a thermal expansion coefficient of the through tube is higher than a thermal expansion coefficient of the casing. The second adhesive is an epoxy adhesive having a Young's modulus after curing of 100 GPa or more and a glass transition temperature of 80 ° C. or more, or an acrylic adhesive having a Young's modulus after curing of 10 GPa or less and a glass transition temperature of 40 ° C. or more. The fiber Bragg grating device according to any one of claims 3 to 7, further comprising:

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