JP2008083281A - Single core bi-directional transmission/reception module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single core bi-directional transmission/reception module that reduces transmission light reflection on the inner wall of a metallic housing and that can obtain stable transmission/reception properties. <P>SOLUTION: A laser diode 3, a photodiode 4, and a wavelength selective filter 8 are mounted on a metallic housing, with the end of optical fibers fixedly structured on the metallic housing or the outer side thereof. Transmission light emitted by the laser diode 3 forms an image on the optical fiber end face through the wavelength selective filter 8, while a signal light emitted from the optical fiber is made incident on the photodiode 4 through the wavelength selective filter 8. This single core bi-directional transmission/reception module is designed to be coated with a light absorbing material 40 that absorbs light of a communication wavelength region emitted by the laser diode 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a single-fiber bidirectional transmission / reception module.

  For example, a structure called a BIDI (bi-directional) type as shown in FIG. 9 is used as a single-fiber bidirectional optical transmission / reception module that transmits optical signals having two different wavelengths for transmission and reception using a single optical fiber. (For example, refer nonpatent literature 1). As shown in FIG. 9, the BIDI type single-core bidirectional transmission / reception module includes, for example, a transmission unit 305 equipped with a laser diode 303 and a laser diode output monitoring photodiode 309, a reception unit 306 equipped with a photodiode 304 and a reception IC 310, The optical fiber 315 is configured to be aligned and fixed to the metal casing 300 in which the wavelength selection filter 308 is built.

  The laser diode 303 and the optical fiber 315 are opposed to each other with the wavelength selection filter 308 interposed therebetween. The wavelength selection filter 308 is inclined 45 degrees with respect to the optical path on the optical path from the laser diode 303 to the optical fiber 315. Has been placed. The laser diode 303 and the photodiode 304 are arranged so that the optical path between the laser diode 303 and the optical fiber 315 is orthogonal to the optical path between the photodiode 304 and the wavelength selection filter 308.

  That is, in the single fiber bidirectional transmission / reception module shown in FIG. 9, the transmission light 320 emitted from the laser diode 304 passes through the wavelength selection filter 308 and forms an image on the end face of the optical fiber 315, and the signal light emitted from the optical fiber 315. Reference numeral 330 is configured to be reflected by the wavelength selection filter 308 and enter the photodiode 304.

"Optical transceiver module for access" OPTRONICS, 2004, No.1, pp.172-176

  However, most of the transmission light 320 emitted from the laser diode 304 is transmitted through the wavelength selection filter 308 and forms an image on the end face of the optical fiber 315, but actually, about 0.1 to 1% of the transmission light 320. A small amount of light (hereinafter referred to as “partially transmitted light”) 320 a does not pass through the wavelength selection filter 308 but is reflected by the wavelength selection filter 308. Thus, the partially transmitted light 320 a reflected by the wavelength selection filter 303 remains in the metal housing 300.

  Further, when the positions of the laser diode 303 and the photodiode 304 are interchanged in the single-core bidirectional transmission / reception module shown in FIG. 9, most of the transmission light from the laser diode is reflected by the wavelength selection filter, and the optical fiber. Although the image is formed on the end face, part of the transmitted light passes through the wavelength selection filter and remains inside the metal casing.

  Further, the partial transmission light 320a reflected or transmitted by the wavelength selection filter 308 is reflected by the inside of the metal casing 300, and a part of the transmission light 320a is transmitted through the wavelength selection filter 308 as shown in FIG. There is a risk of entering the diode 304. As described above, when a part of the transmission light 320a is incident on the signal receiving photodiode 3, there is a problem that the part of the transmission light 320a may become noise and adversely affect the actual signal reception.

  The present invention solves such problems, and an object of the present invention is to provide a single-fiber bidirectional transmission / reception module that can reduce reflection of transmission light by an inner wall of a metal casing and obtain stable transmission / reception characteristics.

  In order to solve the above problems, a single-fiber bidirectional transmission / reception module according to claim 1 of the present invention includes a semiconductor optical transmission element, an optical signal reception element, and a wavelength selection filter mounted on a metal casing. An optical fiber is fixed outside the body, and the transmission light emitted from the semiconductor optical transmission element forms an image on the end face of the optical fiber through the wavelength selection filter, and the signal light emitted from the optical fiber is In the single-fiber bidirectional optical transceiver module that enters the optical signal receiving element through the wavelength selection filter, the metal casing is coated with a light absorbing material that absorbs light in a communication wavelength range on an inner wall. To do.

  The single-fiber bidirectional transmission / reception module according to claim 2 of the present invention is the single-core bidirectional transmission / reception module according to claim 1, wherein the light absorbing material is a polymer containing a C—H bond.

  The single-fiber bidirectional transmission / reception module according to claim 3 of the present invention is the single-core bidirectional transmission / reception module according to claim 1 or 2, wherein the light absorbing material is applied by spin coating.

  According to the above-described single-fiber bidirectional transmission / reception module according to the present invention, the transmission light emitted from the semiconductor optical transmission element is reflected by the wavelength selection filter in a structure that passes through the wavelength selection filter and forms an image on the end face of the optical fiber. A part of the light or a part of the light reflected by the wavelength selection filter and transmitted through the wavelength selection filter in the configuration in which the image is formed on the end face of the optical fiber may be absorbed by the light absorbing material applied to the inner wall of the metal housing. Therefore, it is possible to suppress a part of the transmission light from entering the photodiode.

  As a result, the internal optical crosstalk between the semiconductor optical transmitting element and the optical signal receiving element can be reduced to −47 dB or less, and the signal light with an extinction ratio of 10 dB and an average optical power of −30 dBm can be stabilized. Can be maintained at 48 dB or more necessary for reception. Therefore, the influence of the noise light from the laser diode light on the reception characteristic of the signal light on the photodiode side can be reduced to a level at which it can be ignored.

  Moreover, manufacturing cost can be suppressed by apply | coating the polymer which absorbs infrared rays with a wavelength of 1.0-1.6 micrometers by spin coating etc.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a partial cross-sectional view showing an example of a single-core bidirectional transmission / reception module. As shown in FIG. 1, in this embodiment, the single-core bidirectional transmission / reception module includes a laser diode 3, a metal casing configured by covering a stem 1, which is a support, with a bottomed cylindrical lens cap 2. The photodiode 4 and the wavelength selection filter 8 are accommodated.

  Specifically, the laser diode 3 and the photodiode 4 are fixed on the stem 1 via the subcarriers 5 and 6, respectively, and the wavelength selection filter 8 is held by a holder (not shown). Sealed by a cap 2. It is assumed that an optical fiber (not shown) is fixed outside the lens cap 2 and at a position facing the lens 7.

  The laser diode 3 is arranged so that the outgoing transmission light 20 passes through the wavelength selection filter 8 and passes through the lens 7 and is incident on the end face of the optical fiber. The photodiode 4 is emitted from the optical fiber and passes through the lens 7. The signal light 30 reflected by the wavelength selection filter 8 is arranged so as to be received.

  In the present embodiment, at least the inner wall 2a of the lens cap 2 is coated with a light absorbing material 40 over the entire surface. Examples of a method for applying the light absorbing material 40 to the inner wall 2a of the lens cap 2 include spin coating. In addition, as the light absorbing material 40, a material that prevents reflection of light in the wavelength range of light used as the transmission light 20, for example, in the wavelength range of 1.0 to 1.6 μm, is used according to the communication wavelength range. .

  According to the single-core bidirectional transmission / reception module of the present embodiment, the transmission light 20 emitted from the laser diode 3 passes through the wavelength selection filter 8 and forms an image on the end face of the optical fiber via the lens 7. However, a part of the transmission light 20 a is reflected by the wavelength selection filter 8. Here, since the light absorbing material 40 is applied to the inner wall 2 a of the lens cap 2, the reflected partial transmission light 20 a is absorbed by the light absorbing material 40.

  Accordingly, even when a part of the transmission light 20 emitted from the laser diode 3 is reflected by the wavelength selection filter 8, this light can be absorbed by the inner wall 2a of the lens cap 2, and therefore the photodiode 4 Therefore, there is no possibility that the transmitted light 20a is incident on the light and becomes noise light and has an adverse effect.

  In addition, the film thickness of the light absorption material 40 does not need to be uniform, and should just be able to absorb the light which stayed inside the metal housing. In addition to the method of absorbing the partial transmission light 20a described above, a dielectric multilayer film is coated on the inner wall 2a to reduce the reflection of the partial transmission light 20a and suppress the generation of noise light. What is necessary is just to maintain optical isolation between 20 and the receiving photodiode 4 at 48 dB or more.

  Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIGS. FIG. 2 is a schematic diagram illustrating the transmission unit of the present embodiment, FIG. 3 is a schematic diagram illustrating the reception unit of the present embodiment, FIG. 4 is a schematic diagram illustrating the inside of the single-core bidirectional transmission / reception module of the present embodiment, and FIG. 1 is a cross-sectional view schematically showing a single core bidirectional transmission / reception module of the present embodiment with a part thereof broken away. FIG. Note that this embodiment is an example showing the effects of the present invention, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

  The single-core bidirectional transmission / reception module in this embodiment uses a buried waveguide type DFB-LD having a ridge processing with an oscillation wavelength of 1310 nm as a semiconductor optical transmission element, and a photodiode 104 having a light receiving diameter of 60 μm as an optical signal reception element. Will be described as an example.

  As shown in FIGS. 2 to 5, the single-core bidirectional transmission / reception module of the present embodiment includes a laser diode 103, a pin-photo inside a metal casing configured by covering a stem 101 as a support with a lens cap 102. A diode (hereinafter referred to as a photodiode) 104, a laser diode output monitoring photodiode (MPD) 109, a receiving IC (transimpedance-amplifier: TIA) 110, a chip capacitor 111, and the like are mounted on the lens cap 102. A sleeve 113 containing a 55 μm cut filter 112 is fixed, and a pigtail fiber 115 covered with a fiber collar 114 is fixed on the sleeve 113.

  The laser diode 103 and the laser diode output monitoring photodiode 109 are supported by the subcarrier 105, and the photodiode 104 is supported by the subcarrier 106 and arranged on the stem.

  The subcarrier 105 has a V-groove 105a on the side surface, and the wavelength selection filter 108 is fixed to the V-groove 105a. As a result, the wavelength selection filter 108 is disposed on the side of the laser diode 103 in an inclined state with respect to the vertical direction, and the transmitted light 120 is reflected by the wavelength selection filter 108 as shown in FIG. It is configured to enter the end face of the fiber 115.

  The photodiode 104 is arranged immediately below the wavelength selection filter 108 so that the signal light 130 emitted from the pigtail fiber 115 and transmitted through the wavelength selection filter 108 is incident thereon.

  Furthermore, as shown with dots in FIG. 5, a light absorbing material that absorbs a 1310 nm laser beam is applied to the inner wall 102a of the lens cap 102 except for the lens 107 portion.

  In this embodiment, the optical path length from the wavelength selection filter 108 to the photodiode 104 is 0.55 ± 0.1 mm, and the optical path length from the wavelength selection filter 108 to the laser diode 103 is 0.55 ± 0.1 mm. Designing.

Hereinafter, the assembly process of the single-fiber bidirectional transmission / reception module according to the present embodiment will be described.
First, a transmitter is manufactured. As shown in FIG. 2, the laser diode 103 and the laser diode output monitoring photodiode 109 are fixed on the subcarrier 105 with gold-tin solder. If the laser diode 103 is mounted on the subcarrier 105 by an automatic mounting machine, the mounting accuracy can be mounted with a yield of almost 100% within ± 50 μm with respect to the designated coordinates on the subcarrier 105. Thereafter, the wavelength selection filter 108 is inserted into the V groove portion 105a of the subcarrier 105, and the wavelength selection filter 108 is tilted and fixed with an adhesive.

  Next, the receiving unit is manufactured. As shown in FIG. 3, the photodiode 104 is fixed on the stem 101 with gold-tin solder via the subcarrier 106. The photodiode 104 is mounted by an automatic mounting machine. The mounting accuracy may be within a circle having a radius of 100 μm centered on the designated coordinates on the stem 101, and this accuracy can be achieved with a yield of almost 100%. Next, the receiving IC 110 and the power supply noise cutting chip capacitor 111 are mounted by an automatic mounting machine, and fixed using an adhesive. Finally, the terminals that need to be connected, for example, the chip capacitor 111 and the pin terminal 116 are connected by wire bonding 117 (see FIG. 4).

  Next, the transmission unit is aligned. As shown in FIG. 4, the laser diode 103, the laser diode output monitoring photodiode 109, and the subcarrier 105 on which the wavelength selection filter 108 is mounted are connected to the optical path between the laser diode 103 and the optical fiber 115, and the photodiode 104 to the light. The optical path between the fibers 115 is aligned so as to overlap between the wavelength selection filter 108 and the lens 107, and fixed with gold-tin solder. Note that alignment is performed by moving the subcarrier 105 in the direction indicated by the white arrow in FIG. 4 and adjusting the position.

  Finally, sealing with the lens cap 102 and alignment of the optical fiber 115 are performed. As shown in FIG. 5, a lens cap 102 having an inner wall 102a coated with a 1310 nm absorbing polymer is placed on a stem 101 on which all components have been mounted, and fixed by resistance welding. Next, a sleeve 113 containing a 1.55 μm cut filter 112 is placed on the lens cap 102 and fixed by welding with a YAG laser. Further, the laser diode 103 is energized to emit light, and the pigtail fiber 115 covered with the fiber collar 114 is actively aligned and fixed by welding with a YAG laser.

  In this embodiment, the lens 107 described above may be an aspherical lens or a ball lens. The base of the light absorbing material applied to the inner wall 102a of the lens cap 102 has a refractive index of about 1.5 or less including many C—H bonds such as polyimide, polycarbonate, UV curable resin, and PMMA (Polymethyl methacrylate). A polymer having heat resistance of 85 ° C. or higher is preferable. Furthermore, in order to increase the light absorption efficiency of 1310 nm in these base materials, other polymer compounds having a C—H bond may be mixed and used.

  The transmission light 120 emitted from the laser diode 103 is reflected by the wavelength selection filter 108 and forms an image on the end face of the optical fiber 115, but a small amount of light (hereinafter referred to as partial transmission light) 120a indicated by a broken line in the figure. Passes through the wavelength selection filter 108. According to the present embodiment, since the light absorbing material is applied to the inner wall 102a of the lens cap 102, the partially transmitted light 120a transmitted through the wavelength selection filter 108 is substantially absorbed by the light absorbing material when entering the inner wall 102a. Will be. Therefore, it is possible to reduce the possibility of noise occurring during signal reception by the photodiode 104.

  In the single-fiber bidirectional transmission / reception module manufactured by the above-described process, the optical isolation between the transmission light 120 and the reception photodiode 104 is 48 dB or more, and the transmission from the laser diode is given to the reception characteristic of the signal light on the photodiode side. Noise light due to light can be reduced to such an extent that the influence can be ignored.

  The second embodiment of the present invention will be described in detail with reference to FIGS. FIG. 6 is a cross-sectional view schematically showing the single-core bidirectional transmission / reception module according to this embodiment, and FIG. 7 is a perspective view showing the filter holding holder according to this embodiment.

  As shown in FIG. 6, in this embodiment, the single-fiber bidirectional transmission / reception module includes a laser diode 203, a photodiode 204, and a reception IC 210 in a metal casing configured by covering a stem 201 as a support with a lens cap 202. , And a wavelength selection filter 208. The inner wall 202a of the lens cap 202 is coated with polyimide as a light absorbing material indicated by dots in FIG.

  The laser diode 203 is fixed on the subcarrier 205, and the photodiode 204 is fixed on the stem 201. The wavelength selection filter 208 is installed on the side of the laser diode 203 and above the photodiode 204 so as to straddle the photodiode 204.

  The filter holding holder 218 includes a recess 218a through which signal light 230 emitted from an optical fiber (not shown) passes, and the laser diode 203 is disposed at a height substantially equal to the inner wall portion 218b constituting the recess 218a of the filter holding holder 218. Has been. Like the inner wall 202a of the lens cap 202, polyimide as a light absorbing material is applied to the inner wall portion 218b.

  The laser diode 203 is arranged so that the transmission light 220 is reflected by the wavelength selection filter 208 and passes through the lens 207 and forms an image with the end face of the optical fiber (not shown). The photodiode 204 is emitted from the optical fiber, and the lens 207 and It arrange | positions so that the signal light 230 which permeate | transmitted the wavelength selection filter 208 may be received.

  Most of the transmission light 220 emitted from the laser diode 203 is reflected by the light wavelength selection filter 208, passes through the lens 207, and enters the optical fiber. The partially transmitted light 220a passes through the wavelength selection filter 208 and travels toward the inner wall 218b.

  In this embodiment, since polyimide as a light absorbing material is applied to the inner wall portion 218b and the inner wall 202a, the partially transmitted light 220a emitted from the laser diode 203 and transmitted through the wavelength selection filter 208 is almost absorbed by the polyimide. Will be. As a result, it is possible to suppress the light in the transmission wavelength range from entering the photodiode 204 as noise, and it is possible to reduce the influence of the partial transmission light 220a on the reception characteristics of the photodiode 204.

  That is, according to the present embodiment, the internal optical crosstalk between the laser diode and the photodiode can be set to −47 dB or less, and the optical isolation amount is stabilized with the signal light having the extinction ratio of 10 dB and the average optical power of −30 dBm. It can be maintained at 48 dB or more necessary for reception. Therefore, the influence of the noise light from the laser diode light on the reception characteristic of the signal light on the photodiode side can be reduced to a level at which it can be ignored.

  A third embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a cross-sectional view schematically showing the single-core bidirectional transmission / reception module according to this embodiment. In this embodiment, the present invention is applied to a BI-DI type module, and the description of the same members as those shown in FIG. 9 will be omitted as appropriate, and different members will be mainly described.

  As shown in FIG. 8, the single-fiber bidirectional transmission / reception module according to this embodiment includes a transmission unit 305 equipped with a laser diode 303, a reception unit 306 equipped with a photodiode 304, and an optical fiber 315. It is configured to be aligned and fixed to a built-in metal casing 301. The inner wall 301a of the metal casing 301 is coated with PMMA as a light absorbing material on the entire surface.

  According to the present embodiment, most of the transmission light 320 emitted from the laser diode 303 passes through the wavelength selection filter 308 and forms an image on the end face of the optical fiber 315, and the partial transmission light 320a indicated by a broken line in the figure has a wavelength. The light is reflected by the sorting filter 308 and enters the inner wall 301 a of the metal casing 301. Since the inner wall 301a is coated with PMMA as a light absorbing material, the partially transmitted light 320a incident on the inner wall 301a is almost absorbed by the PMMA applied to the inner wall 301a.

  Thereby, there is no possibility that the partial transmission light 320a emitted from the laser diode 303 and reflected by the wavelength selection filter 308 is incident on the photodiode 304 as noise light, and the influence on the reception characteristics of the photodiode 304 is reduced. Became possible.

  That is, the internal optical crosstalk between the laser diode and the photodiode can be set to −47 dB or less, and it is necessary for stably receiving signal light having an optical isolation amount of 10 dB and an average optical power of −30 dBm. It can be maintained at 48 dB or more. Therefore, it is possible to reduce the influence of noise light from the laser diode light on the reception characteristics of the signal light on the photodiode side to a level at which it can be ignored.

  The present invention is applicable to a single-fiber bidirectional transmission / reception module.

It is sectional drawing which shows typically the single core bidirectional | two-way transmission / reception module which concerns on embodiment of this invention. It is a perspective view which shows typically the transmission part of the single core bidirectional | two-way transmission / reception module in Example 1 of this invention. It is a perspective view which shows typically the receiving part of the single core bidirectional | two-way transmission / reception module in Example 1 of this invention. It is a perspective view which shows typically a part of single fiber bidirectional | two-way transmission / reception module in Example 1 of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view schematically showing a part of a single-core bidirectional transmission / reception module according to Embodiment 1 of the present invention. It is sectional drawing which shows typically the single core bidirectional | two-way transmission / reception module in Example 2 of this invention. It is a perspective view which shows the filter holding holder of the single core bidirectional | two-way transmission / reception module in Example 2 of this invention. It is sectional drawing which shows typically the single core bidirectional | two-way transmission / reception module in Example 3 of this invention. It is sectional drawing which shows the example of the conventional single core bidirectional | two-way transmission / reception module.

Explanation of symbols

1, 101, 201 Stem 2, 102, 202 Lens cap 2a, 102a, 202a, 301a Inner wall 3, 103, 203, 303 Laser diode 4, 104, 204, 304 Photo diode 5, 6, 105, 106, 205 Subcarrier 7, 107, 207 Lens 8, 108, 208, 308 Wavelength selection filter 9, 109 Laser diode output monitoring photodiode 10, 110 Receiver IC
11 Chip capacitor 12 1.55 μm cut filter 13 Sleeve 14 Fiber collar 15 Pigtail fiber 16 Terminal 17 Wire bonding 20, 120, 220, 320 Transmitted light emitted from laser diode 30, 130, 230, 330 Emitted from optical fiber Signal light 40 Light absorber

Claims (3)

  A semiconductor optical transmission element, an optical signal receiving element, and a wavelength selection filter are mounted on a metal casing, and an end portion of an optical fiber is fixed to the metal casing or the outside of the metal casing, and the semiconductor Transmission light emitted from the optical transmission element forms an image on the end face of the optical fiber through the wavelength selection filter, and signal light emitted from the optical fiber enters the optical signal reception element through the wavelength selection filter. In the single-fiber bidirectional optical transceiver module, a light-absorbing material that absorbs light in a communication wavelength region emitted from the semiconductor optical transmission element is applied to the inner wall of the metal casing.   The single-fiber bidirectional transmission / reception module according to claim 1, wherein the light absorbing material is a polymer containing a C—H bond.   The single-fiber bidirectional transmission / reception module according to claim 1 or 2, wherein the light absorbing material is applied by spin coating.

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