JP2007173498A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a sufficient cooling temperature in a cooling APD module for use in quantum encryption communication, and to prevent the deterioration of the characteristics of an APD module etc. <P>SOLUTION: A cooling element such as a Peltier element 7 on which an optical element such as a mounted APD element 3 is received in a package 5 wherein nitrogen or xenon is sealed, and the optical element is optically coupled outside the package 5 using optical coupling members 1, 2, and 4. Because the APD element 3 is arranged on the Peltier element 7 to be in direct contact with it, the APD element 3 can be cooled down efficiently to obtain the maximum cooling temperature of -62°C which has been improved by 20°C or more as compared to the conventional article. Because the optical axis adjustment is carried out in a state of the APD element 3 cooled down to the temperature in a real usage state thereof, the change of the characteristics is reduced due to the temperature change in the cooled state in real usage, so that the deterioration can be prevented in the coupling efficiency due to the displacement of the optical axis upon cooling. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical module, and more particularly to an optical module such as a cooled APD module used for quantum cryptography communication.

  Conventionally, in an optical fiber gyro apparatus, the output noise and thermal noise of a light receiving element increase corresponding to an increase in the absolute temperature. Therefore, as shown in FIG. 2, when cooling the light receiving element and keeping it at a low temperature, for example, Patent Document 1 discloses a winding frame 103b in which an optical fiber 103a is wound many times on the base 100. An optical fiber loop 103 is attached, the light receiving element 102 is attached in the opening 101a of the block 101, and the block 101 is attached in the winding frame 136 of the base 100 via a cooling device 104 such as a Peltier element.

  The Peltier element 104 is driven by the direct current 105, cools the block 101, and keeps the light receiving element 102 at an extremely low temperature, thereby reducing the output noise of the light receiving element 102 and increasing the S / N ratio of the apparatus. The sensitivity as a gyro device can be greatly improved.

On the other hand, as shown in FIG. 3, the cooling type APD module used for conventional quantum cryptography communication has an APD element 13 mounted on a CAN package 17 and a coupling lens 14 and a ferrule 12 at the tip at room temperature. After adjusting and fixing each of the optical fibers 11 to form an optical module, the APD element 13 was cooled on the Peltier element 18 fixed in the package 15 via a copper cutting block 16 having high thermal conductivity. .
JP-A 63-159712

  However, in the optical fiber gyro apparatus described in Patent Document 1, since the light receiving element 102 is cooled by the Peltier element 104 via the block 101, the heat conduction is saturated and the light receiving element 102 cannot be sufficiently cooled. was there.

  In the cooling type APD module described above, similarly, the APD element 13 itself is not in direct contact with the Peltier element 18, the heat conduction is saturated, and the APD element 13 cannot be sufficiently cooled. there were.

  Further, in the conventional cooled APD module, the APD element 13 disposed in the CAN package 17 and the optical fiber 11 and the coupling lens 14 in which the ferrule polished at an angle of 5 degrees is disposed at the tip are formed into an optical module at room temperature. Therefore, due to the difference in thermal expansion of the member due to temperature change, there is a problem that the optical axis shift occurs at the time of cooling at −50 ° C. or lower, which is the actual use state, and the coupling efficiency is deteriorated.

  Accordingly, the present invention has been made in view of the above-described problems in the prior art, and can sufficiently cool the light receiving element of the optical fiber gyro device, the APD element of the cooling type APD module, etc. An object of the present invention is to provide an optical module in which the optical axis does not shift and the coupling efficiency does not deteriorate.

  In order to achieve the above object, the present invention provides an optical module in which a cooling element on which an optical element is mounted is accommodated in a package enclosing nitrogen or xenon, and the optical element is disposed outside the package. Are optically coupled using an optical coupling member. Here, the optical element may be an APD element, the cooling element may be a Peltier element, and the optical coupling member may be a coupling lens and an optical fiber.

  According to the present invention, since the APD element is arranged so as to be in direct contact with the Peltier element, the APD element can be efficiently cooled, and the maximum cooling temperature is −62 ° C., which is 20 ° C. or higher compared to the conventional product. Improvements can be made.

  In addition, since the optical axis adjustment is performed with the APD element cooled to the temperature in the actual use state, the change in characteristics due to the temperature change in the actual use cooling state can be reduced, and the optical axis is shifted and coupled during cooling. It is possible to prevent the efficiency from deteriorating.

  Furthermore, since only the APD element is cooled, the Peltier element to be used can be reduced in size, and since no optical components are arranged inside the package, the volume of the package is reduced to about 1/2 of the conventional volume. can do.

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

  FIG. 1 shows an embodiment of an optical module according to the present invention. This optical module has a sensitivity in a wavelength band of 1550 nm and converts an optical signal into an electric signal (photocurrent) (InGaAs-APD (avalanche photo)). Diode) The element 3 is made of a low temperature solder, silver paste or the like on the Peltier element 7 that allows sufficient cooling so that the temperature becomes -50 ° C. or less, and the light receiving surface of the APD element 3 is firmly prevented from being damaged by heat. Stick. Further, the thermistor 10 for temperature measurement is similarly fixed to the upper part of the Peltier element 7 by using low temperature solder, silver paste or the like.

  The Peltier element 7 having the APD element 3 and the thermistor 10 fixed to the upper part is fixed to a predetermined position of the package 5 having a hermetic structure around it using a low temperature solder. The package 5 has terminals hermetically sealed with glass in order to input an electric signal from the outside and to output an electric signal from the APD element 3, and the APD element 3 and the thermistor 10 are bonded together by bonding. The Peltier element 7 is joined to each terminal by a soldering method via a lead wire.

  The package 5 assembled as described above is tightly seam welded to the surroundings using a cover in a nitrogen atmosphere or a xenon atmosphere having a low thermal conductivity, and the airtightness inside the package 5 is maintained. Here, in order to optically couple the light receiving surface of the APD element 3 inside the package 5 from the outside, the window glass 6 made of BK-7 that has been optically polished at an angle of 5 degrees in consideration of the reflection suppression of the signal light is packaged. In order to keep hermetic with 5, it is fixed with low melting point glass.

  The optical fiber 1 for the purpose of propagating signal light has a ferrule 2 that is optically polished at an angle of 5 degrees at the tip in order to suppress reflected light, and is used for optical coupling with the light receiving surface of φ30 μm of the APD element 3. Adjust the X, Y, and Z axes of the ferrule 2 and the coupling lens 4 with a manipulator via the coupling lens 4 (in this embodiment, a GRIN lens is used), and adjust them to the optimal position with respect to the light receiving surface. Condensed light is combined.

  The ferrule 2 and the coupling lens 4 respectively adjusted to the optimum coupling position are firmly fixed to the package 5 by the UV adhesive 9 via the glass support 8. The signal light that is optimally focused and incident on the light receiving surface of the APD element 3 is converted from an optical signal into an electric signal in the APD element 3 and output as a photocurrent to a terminal outside the package 5. In the present invention, by providing an optical component outside the package 5, unlike the conventional structure in which the optical component is arranged inside the package, a cooled APD module that is particularly excellent in performance and reliability is provided. be able to.

  Next, the operation of the optical module having the above configuration will be described.

  As shown in FIG. 1, the signal light guided from the connector side of the optical fiber 1 is emitted from a ferrule 2 that is optically polished at an angle of 5 degrees to suppress reflection at the other end. The signal light emitted from the ferrule 2 is incident on the coupling lens 4 that enables condensing and coupling because the outgoing beam is expanded as it is. The signal light that is optimally collected and incident on the light receiving surface of the APD element 3 is converted into an electrical signal from the optical signal and output to a terminal outside the package 5 as a photocurrent.

  In order to set the temperature of the APD element 3 in the package 5 to −50 ° C. or less effective for quantum encryption communication, the APD element 3 is placed on the Peltier element 7 composed of two stages of the low temperature side and the high temperature side. Fix using low-temperature solder, silver paste, etc. In order to measure the actual temperature of the APD element 3, the thermistor 10 is also fixed in the vicinity of the APD element 3 on the Peltier element 7 with low-temperature solder, silver paste, or the like.

  The Peltier element 7 to which the APD element 3 and the thermistor 10 are fixed is fixed to a predetermined position in the package 5 with low-temperature solder, and the reverse voltage is input to the APD element 3 from the outside of the package 5 and the voltage applied to the Peltier element 7 In order to output a resistance value for measuring the photocurrent from the APD element 3 and the temperature of the thermistor 10 for the purpose of inputting the APD element 3, the APD element 3, the thermistor 10, and the Peltier element 7 have terminals hermetically sealed with glass. Are joined to the terminals.

  The boundary surface between the package 5 and the coupling lens 4 is provided with a BK-7 window glass 6 processed obliquely at 5 degrees in order to suppress reflection, and is fixed by the package 5 and the low melting point glass. Airtightness is maintained.

  The package 5 to which the Peltier element 7 or the like is fixed has a low thermal conductivity in a nitrogen or xenon atmosphere, uses a cover made of the same material as the package 5, and is seam welded to maintain hermeticity throughout the interior of the package 5. ing.

  In order to optically couple with the φ30 μm light receiving surface of the APD element 3 from the outside of the package 5, the signal light guided from the connector side of the optical fiber 1 is optically polished at an angle of 5 degrees to suppress reflection at the other end. The light is emitted from the ferrule 2 and is incident on a coupling lens 4 that enables condensing and coupling of the emitted beam.

  The ferrule 2 and the coupling lens 4 are attached to a manipulator so that adjustment in the X, Y, and Z directions is possible, and light is optimally applied to the light receiving surface of φ30 μm of the APD element 3 disposed inside the package 5. After each manipulator is adjusted for the purpose of bonding, the manipulator is firmly fixed to the package 5 with the UV adhesive 9 through the glass support 8.

  The signal light that is optimally collected and incident on the light receiving surface of the APD element 3 is converted into an electrical signal from the optical signal in the APD element 3 and is output to a terminal outside the package 5 as a photocurrent.

  The present invention can be applied to a light receiving module that is operated at a low temperature or a high temperature constant temperature, a light emitting module typified by an LD module, and the like, similarly to the above optical module.

It is a figure which shows the APD module as one Embodiment of the optical module concerning this invention, Comprising: (a) is a top view, (b) is the sectional view on the AA line of (a). It is sectional drawing which shows an example of the conventional optical fiber gyro apparatus. It is a figure which shows an example of the conventional cooling type APD module, (a) is a top view, (b) is a side view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Ferrule 3 APD element 4 Coupling lens 5 Package 6 Window glass 7 Peltier element 8 Glass support 9 UV adhesion 10 Thermistor 11 Optical fiber 12 Ferrule 13 APD element 14 Coupling lens 15 Package 16 Cutting block 17 CAN package 18 Peltier element

Claims (2)

  A cooling element on which an optical element is mounted is accommodated in a package in which nitrogen or xenon is enclosed, and the optical element is optically coupled using an optical coupling member outside the package. Optical module.   The optical module is an APD element, the cooling element is a Peltier element, and the optical coupling member is a coupling lens and an optical fiber.

Images