JP2005045145A - Optical module and transmitting/receiving circuit for optical communication using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To alleviate the strain of a transmitting light waveform and to facilitate impedance matching of receiving signal wiring in an optical module in which a photodetector and a light emitting element are mounted. <P>SOLUTION: The optical module includes receiving terminals (9c, 9d) for retrieving a received electrical signal of a PD (3) of the photodetector to an exterior and derived from the end of a cavity (1). Meanwhile, the optical module also includes transmitting terminals (10c, 10d) for supplying a transmitting electrical signal to the LD (4) of the light emitting element and projected from the rear surface (1B) of the cavity (1) almost directly under the LD (4), and connected to the LD (4) via a through hole. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical module that transmits and receives optical signals and an optical communication transceiver circuit using the same, and more particularly to a light receiving element and a light emitting element mounted in one package.

  Along with the widespread use of optical access services, devices that provide optical communication services are required to reduce the installation area by miniaturization, to save power by sharing parts, and to reduce the cost of assembling optical module substrates. In particular, the optical module occupies a large area in the apparatus, and mounting a plurality of optical modules at a high density greatly contributes to the solution of the above problems.

  FIG. 6 is a configuration diagram of a general optical transmission / reception circuit used for optical communication. In this configuration, since transmission / reception is performed with one optical fiber, the fiber cost can be reduced. In FIG. 6, the optical module 20 has a package cavity 21. The package cavity 21 includes a PD (Photo Diode) 23 which is a light receiving element, an LD (Laser Diode) 24 which is a light emitting element, an optical waveguide 25, and a WDM (Wavelength Division Multiplex) filter. 26, a preamplifier 27, and a monitor PD 28 are mounted.

  At the time of transmission, the LD drive circuit 31 supplies an electrical signal to the LD 24, and the LD 24 emits light according to the supplied electrical signal. The optical signal output from the LD 24 is input to the optical fiber. Here, the monitoring PD 28 converts the optical signal output from the LD 24 into an electrical signal. The LD drive circuit 31 monitors the electrical signal detected by the monitor PD 28 and adjusts the LD output. The PD 23 converts an optical signal incident from the optical fiber into an electrical signal. The electrical signal output from the PD 23 is amplified by the preamplifier 27 and then amplified and shaped by the post-amplifier circuit 32.

In such a configuration in which a plurality of optical transceiver circuits are mounted, as a condition for maintaining the quality of the output waveform such as low distortion,
(1) In order to ensure isolation between transmission and reception, not only one channel but also signal wiring of each channel is arranged with a certain interval or more,
(2) The inductance of the wiring from the light emitting element drive circuit to the light emitting element is sufficiently small and uniform between channels so as not to cause ringing or waveform distortion in the transmitted light waveform.
(3) In order to improve the electrical characteristics of the received high-frequency signal, the impedance of the external circuit must be matched and uniform between channels.
Is mentioned.

  On the other hand, the form of a package on which a semiconductor element, an optical waveguide, an integrated circuit and the like in optical communication are mounted is generally divided into two types. One is a structure using a structure called DIP (Dual Inline Package), QFP (Quad Flat Package) or the like as shown in FIG. For example, as shown in Non-Patent Document 1, etc., butterfly-type lead terminals 40 are provided on the sides of the package. This configuration is simple because the wiring between the integrated circuit inside the package and the lead terminal 40 is realized by lead metal, and is excellent in strength and heat dissipation. The other one uses structures called PGA (Pin Grid Array) and BGA (Ball Grid Array) as shown in FIG. For example, as shown in Non-Patent Document 2, etc., a rod-like or spherical lead terminal 50 is provided on the bottom surface of the package. A multilayer substrate is generally used for wiring between the integrated circuit inside the package and the lead terminals 50. In such a package, since the lead terminals 50 can be arranged in a plane, it is possible to secure a larger number of terminals compared to DIP or QFP.

  When these optical modules are mounted on a printed circuit board with a plurality of channels, there are the following problems.

  In an optical module having a DIP or QFP structure, a mounting interval in consideration of wiring margin on a lead terminal or a printed circuit board is necessary, and it is difficult to mount at high density. Further, since the lead terminals of the adjacent optical modules are adjacent to each other, it is necessary to provide a relatively large mounting interval in order to ensure isolation between the reception signal terminal and the transmission signal terminal.

  On the other hand, unlike the DIP and QFP, the PGA and BGA optical modules do not have lead terminals outside the sides of the package, so that the packages can be mounted side by side with high density. However, since it is necessary to use a large number of through holes in the package, the wiring becomes complicated and it is difficult to perform impedance matching over a wide band in order to maintain the electrical characteristics of the received signal.

  A method of achieving a small size and high density by mounting a plurality of channels in one optical module package is also conceivable.

  However, when DIP or QFP is used, lead terminals can be secured only on the four sides of the package. Furthermore, a space for connecting optical fibers is also required. At this time, it is necessary to wire the signal wiring of the channel existing in the center of the package to the side of the package. For this reason, with respect to the transmission signal wiring, the inductance component increases as the wiring length increases. Further, when the line length is different for each channel, the inductance of each channel becomes non-uniform, and the characteristics of each channel become non-uniform. Further, for example, Non-Patent Document 3 and the like also show an example of package mounting of a plurality of channels. However, since the positional relationship between the lead terminal on the transmission side and the lead terminal on the reception side differs for each channel, the characteristics of each channel are It becomes non-uniform.

On the other hand, in the case of using BGA and PGA, by providing a lead terminal directly under the internal element, the restriction on the size of the package due to the number of terminals can be reduced, and the inductance component due to the wiring length can be kept small. However, as mentioned above, through-holes are often used when connecting the integrated circuit inside the package and the lead terminals, so the wiring becomes complicated, and impedance matching over a wide band is required to maintain the electrical characteristics of the high-frequency signal on the receiving side. Is difficult.
Hashimoto et al., IEEE Journal Lightwave Technology, Vol.18, No.11, pp.1541-1546 Takai et al., 2000 Electronic Components and Technology Conference, pp.491-496 Nakanishi et al., IEICE Society Conference, C-3-18, 2002

  The present invention has been made in view of the above circumstances, and an object thereof is an optical module capable of reducing distortion of a transmission optical waveform and facilitating impedance matching of a reception signal wiring, and optical communication using the optical module. It is to provide a transmission / reception circuit.

  A first invention for solving the above-described problems and achieving the object includes a base including a mounting surface and a back surface thereof, a light receiving element that is mounted on the mounting surface and receives an optical signal input from the outside. A light emitting element mounted on the mounting surface for generating an optical signal output to the outside, a receiving terminal for taking out an electric signal from the light receiving element drawn out from an end of the base, and a light emitting element of the light emitting element An optical module having a transmitting terminal for supplying an electric signal to the light emitting element, which is provided in the vicinity of directly below and protrudes from the back surface and is connected to the light emitting element through a through hole.

  According to a second aspect of the present invention, in the first aspect, the base is a substantially rectangular parallelepiped, and the receiving terminal is drawn out from only one side of the base, and the optical signal is applied only to the side facing the side. Input / output ports are provided.

  In a third aspect based on the second aspect, the light emitting element is provided in the vicinity of a side facing a side from which the receiving terminal is drawn.

  According to a fourth invention, in the second or third invention, the set of the light receiving element, the light emitting element, the receiving terminal, and the transmitting terminal is substantially the same, and the receiving terminal A plurality of the substrates are arranged along the arrangement direction.

  The fifth invention is the invention according to any one of the first to fourth inventions, wherein the base, the light receiving element, and the light emitting element are accommodated in a package having an optical fiber connection portion to which an optical fiber is connected, The light emitting element and the light receiving element are connected to the optical fiber connecting portion by an optical waveguide mounted on the mounting surface of the base.

  According to a sixth aspect of the present invention, there is provided a substrate having a conductive layer sandwiched between insulating layers, an optical module according to any one of the first to fifth aspects mounted on the substrate, and the same surface as the optical module. And an amplifier circuit that amplifies and shapes an electrical signal output from the light receiving element, and a drive circuit that is mounted on the back surface of the surface on which the optical module is mounted and that supplies the electrical signal to the light emitting element. It is a communication transceiver circuit.

  According to the present invention, since the receiving terminal is pulled out from the end of the base, impedance matching of the reception signal wiring can be facilitated. In addition, since the transmission terminal is provided near the light emitting element and connected to the light emitting element through the through hole, the length of the transmission signal wiring is shortened. For this reason, the inductance due to the transmission signal wiring can be suppressed, and the distortion of the transmission light waveform can be reduced.

  Exemplary embodiments of an optical module according to the present invention and an optical communication transceiver circuit using the same will be described below in detail from the first embodiment to the third embodiment with reference to the accompanying drawings. .

(First embodiment)
FIG. 1 is an external perspective view showing the configuration of the optical module according to the present embodiment. FIG. 1 shows a single-core WDM bidirectional optical module 100. However, the optical module according to the present invention may be one in which two single-core unidirectional optical fibers are connected.

  In FIG. 1, an optical module 100 has a package cavity (hereinafter referred to as a cavity) 1 which is a substantially rectangular base. One side of the cavity 1 is provided with an optical fiber connection portion 2 connected to an external optical fiber F. On the mounting surface 1A of the cavity 1, a light receiving element PD3 that receives an optical signal input from the optical fiber F and an LD4 that is a light emitting element that generates an optical signal output to the optical fiber F are mounted. Has been. In this embodiment, LD4 is installed in the vicinity of the edge | side in which the optical fiber connection part 2 is provided. PD3 and LD4 are connected to the optical fiber connection portion 2 by an optical waveguide 5 mounted on the mounting surface 1A. In this embodiment, since single-core bidirectional communication is performed, a WDM filter 6 for separating upstream and downstream optical signals is installed in the path of the optical waveguide 5. However, in an optical module in which two single-core unidirectional optical fibers are connected, the WDM filter 6 can be omitted.

  In addition to these, on the mounting surface 1A of the cavity 1, a preamplifier 7 for amplifying an electric signal output from the PD 3 and a monitor PD 8 for detecting the intensity of the optical signal output from the LD 4 are mounted. . However, the preamplifier 7 and the monitor PD 8 can be omitted. For example, the preamplifier 7 may be omitted when the photoelectric conversion efficiency of the PD 3 is high, and the monitoring PD 8 may be omitted when the light emission characteristics of the LD 4 are stable.

  The reception-side terminal 9 related to reception is a butterfly-type lead terminal and is drawn out from the end of the cavity 1. In the present embodiment, the optical fiber connection portion 2 is drawn out only from the side facing the side. Here, the receiving terminal 9 has a PD power supply terminal 9a for connecting the PD 3 and an external power supply (not shown), and a preamplifier power supply for connecting the preamplifier 7 and an external power supply (not shown). A terminal 9b, a pair of receiving terminals 9c and 9d for taking out an electric signal from the PD 3 to the outside, and a grounding terminal 9e are included. The PD power supply terminal 9a, the preamplifier power supply terminal 9b, and the reception terminals 9c and 9d are arranged along the surface of the mounting surface 1A, and are connected to the PD3 and the preamplifier 7 by lead metal.

  FIG. 2 is a cross-sectional view showing wiring on the transmission side of the optical module 100 according to the present embodiment. In FIG. 2, the transmission-side terminal 10 related to transmission is provided so as to protrude from the back surface 1 </ b> B of the cavity 1. Here, a pair of monitor terminals 10a and 10b for connecting the monitor PD 8 and an external LD drive circuit (not shown) and the LD 4 and an external LD drive circuit are connected to the transmission side terminal 10. A pair of transmission terminals 10c and 10d for the purpose is included. The monitor terminals 10a and 10b are provided in the vicinity immediately below the monitor PD 8, and the transmission terminals 10c and 10d are provided in the vicinity immediately below the LD4. The pair of monitoring terminals 10a and 10b are connected to the monitoring PD 8 through through holes 1a and 1b provided in the thickness direction of the cavity 1, and the pair of transmission terminals 10c and 10d are through-holes. It is connected to the LD 4 through the holes 1c and 1d.

  The optical module 100 is mounted on a printed circuit board or the like in the mounting direction indicated by the arrow X in FIG.

  Hereinafter, an operation procedure of the optical module 100 having the above configuration will be briefly described.

  First, the operation during transmission will be described. An electric signal is supplied to the LD 4 from an external LD drive circuit via the transmission terminals 10c and 10d. The LD 4 emits light according to the supplied electric signal, and the optical signal output from the LD 4 is output to the optical fiber F through the optical waveguide 5. The monitoring PD 8 converts the output light of the LD 4 into an electrical signal and outputs this electrical signal to the LD drive circuit. The LD drive circuit adjusts the electrical signal supplied to the LD 4 according to the electrical signal received from the monitoring PD 8.

  Next, the operation during reception will be described. The optical signal that has entered the optical fiber connector 2 from the optical fiber F passes through the optical waveguide 5 and enters the PD 3. The PD 3 converts the incident optical signal into an electrical signal and outputs this electrical signal to the preamplifier 7. The preamplifier 7 amplifies the electrical signal received from the PD 3 and outputs the amplified electrical signal to the outside via the reception terminals 9c and 9d.

  According to the optical module 100 according to the present embodiment, the following effects can be obtained.

  (A) Since the receiving terminals 9c and 9d are pulled out from the end of the cavity 1, it becomes possible to adopt a coplanar structure by arranging grounding terminals on both sides of the receiving terminals 9c and 9d. Matching of impedance in connection with can be facilitated.

  (B) Since the transmission terminals 10c, 10d are arranged near the LD4 and the transmission terminals 10c, 10d and LD4 are connected via the through holes 1c, 1d, the transmission terminals 10c, 10d and LD4 are connected to each other. The wiring length between them can be shortened. As a result, the inductance due to the wiring between the transmission terminals 10c, 10d and the LD 4 can be reduced, and the waveform distortion of the transmission light waveform can be suppressed.

  (C) Since the LD 4 is mounted in the vicinity of the side opposite to the side where the receiving terminals 9c and 9d are provided, the interval between the transmitting terminals 10c and 10d and the receiving terminals 9c and 9d can be increased. Isolation of electrical signals from each other can be ensured.

  (D) FIG. 3 shows an arrangement example when the optical module 100 according to the present embodiment is mounted in multi-channel. As can be seen from FIG. 3, the receiving terminal 9 exists only on one side h of the cavity 1 and the optical fiber connection portion 2 exists only on the side i opposite to the side h. , K have no terminals or the like. For this reason, the other optical module 100 can be mounted close to the sides j and k on both sides of the optical module 100, and high-density mounting is possible. In addition, since the configuration of each optical module 100 is the same, the characteristics of each channel are uniform.

(Second Embodiment)
Since the optical module according to the present embodiment is almost the same as the optical module 100 according to the first embodiment, the same reference numerals are used for portions that are the same as those in the first embodiment. Will be omitted.

  FIG. 4 is an external perspective view showing the configuration of the optical module according to the present embodiment. The optical module 200 shown in FIG. 4 has a plurality of channels accommodated in one package. Specifically, a plurality of transmission / reception units 201 to 204 corresponding to a plurality of channels are mounted in one cavity 210. Here, each of the plurality of transmission / reception units 201 to 204 has substantially the same configuration, and has the same configuration as the optical module 100 according to the first embodiment. Further, the plurality of transmission / reception units 201 to 204 are arranged in the cavity 210 along the arrangement direction (arrow Y direction) of the reception side terminal 9.

  According to the optical module 200 according to the present embodiment, the following effects can be obtained in addition to the effects (A) to (C).

  (E) Since a plurality of transmission / reception units 201 to 204 corresponding to a plurality of channels are mounted in one cavity 210, further high-density mounting is possible.

  (F) Since the configuration of each of the transmission / reception units 201 to 204 is substantially the same, that is, the set of PD3, LD4, reception terminals 9c and 9d, and transmission terminals 10c and 10d are arranged in substantially the same configuration. The characteristics between channels are uniform.

(Third embodiment)
Since the optical communication transceiver circuit according to the present embodiment uses the optical modules 100 and 200 according to the first or second embodiment, the parts common to the first or second embodiment are described. The same reference numerals are used, and the description is omitted.

  FIG. 5 is a cross-sectional view showing the configuration of the optical communication transceiver circuit according to the present embodiment. In FIG. 5, the optical communication transceiver circuit 300 includes a multilayer printed circuit board 310 which is a substrate in which a conductive layer 312 is sandwiched between insulating layers 311 and 313. Here, the conductive layer 312 is grounded.

  The optical module 320 according to the first or second embodiment is mounted on the surface 310A of the multilayer printed circuit board 310. Further, a post-amplifier circuit 330 for amplifying and shaping an electric signal output from the PD 3 of the optical module 320 is mounted on the surface 310A. On the other hand, on the back surface 310B, an LD driving circuit 340 for supplying an electric signal to the LD 4 is mounted in the immediate vicinity of the transmission terminals 10c and 10d.

  The receiving terminals 9c and 9d of the optical module 320 are connected to the post-amplifier circuit 330 through a wiring pattern on the surface 310A. On the other hand, the transmission terminals 10c and 10d project from the back surface 310B through through-holes provided in the thickness direction of the multilayer printed circuit board 310, and are connected to the LD drive circuit 340 via the wiring pattern on the back surface 310B. Yes.

  According to the transmission / reception circuit for optical communication according to the present embodiment, in addition to the effects (A) to (F), the following effects can be obtained.

  (G) Since the post-amplifier circuit 330 is mounted on the front surface 310A and the LD drive circuit 340 is mounted on the back surface 310B with the grounded conductive layer 312 interposed therebetween, transmission and reception isolation is achieved as the entire optical communication transceiver circuit 300. High-density mounting can be realized while ensuring the above.

  (G) Since the LD driving circuit 340 is disposed in the immediate vicinity of the transmission terminals 10c and 10d, the distance from the LD driving circuit 340 to the LD 4 can be shortened. Thereby, the inductance of the wiring from the LD driving circuit 340 to the LD 4 can be reduced.

  As mentioned above, although the optimal form for implementing this invention was shown, it cannot be overemphasized that this invention is not limited to said form.

It is an external appearance perspective view which shows the structure of the optical module which concerns on 1st Embodiment. It is sectional drawing which shows the wiring by the side of the transmission of the optical module which concerns on 1st Embodiment. It is an example of arrangement | positioning in case the optical module which concerns on 1st Embodiment is mounted in multichannel. It is an external appearance perspective view which shows the structure of the optical module which concerns on 2nd Embodiment. It is a cross-sectional view showing a configuration of a transmission / reception circuit for optical communication according to a third embodiment. It is a block diagram of the general optical transmission / reception circuit used for optical communication. It is an external appearance perspective view which shows the structure of the optical module which has a DIP structure. It is an external appearance perspective view which shows the structure of the optical module which has PGA structure.

Explanation of symbols

100 Optical module 1 Package cavity (cavity)
1A Mounting surface 1B Back surface 1a, 1b, 1c, 1d Through hole 2 Optical fiber connection 3 PD
4 LD
5 Optical waveguide 6 WDM filter 7 Preamplifier 8 PD for monitor
DESCRIPTION OF SYMBOLS 9 Reception side terminal 9a PD power supply terminal 9b Preamplifier power supply terminal 9c, 9d Reception terminal 9e Grounding terminal 10 Transmission side terminal 10a, 10b Monitor terminal 10c, 10d Transmission terminal F Optical fiber 200 Optical module 201-204 Transmission / reception Part 210 Cavity 300 Transceiver circuit for optical communication 310 Multilayer printed circuit board 310A Front surface 310B Back surface 311 and 313 Insulating layer 312 Conductive layer 320 Optical module 330 Post-amplifier circuit 340 LD drive circuit

Claims (6)

A substrate having a mounting surface and a back surface thereof;
A light receiving element mounted on the mounting surface and receiving an optical signal input from the outside;
A light emitting element that is mounted on the mounting surface and generates an optical signal that is output to the outside; and a receiving terminal that is pulled out from an end of the base body and takes out an electrical signal from the light receiving element;
A transmission terminal for supplying an electrical signal to the light emitting element, provided to protrude from the back surface near the light emitting element and connected to the light emitting element through a through hole;
An optical module comprising: The said base | substrate is a substantially rectangular parallelepiped, The said receiving terminal is withdraw | derived from only one side of the said base | substrate, The input / output port of the said optical signal is provided only in the side facing the said side. The optical module according to 1. The optical module according to claim 2, wherein the light emitting element is provided in the vicinity of a side opposite to a side from which the receiving terminal is drawn. A set of the light receiving element, the light emitting element, the reception terminal, and the transmission terminal are arranged in the base body along the arrangement direction of the reception terminals with substantially the same configuration. The optical module according to claim 2 or 3. The base, the light receiving element, and the light emitting element are accommodated in a package having an optical fiber connection portion to which an optical fiber is connected,
5. The optical module according to claim 1, wherein the light emitting element, the light receiving element, and the optical fiber connecting portion are connected by an optical waveguide mounted on a mounting surface of the base. A substrate in which a conductive layer is sandwiched between insulating layers;
The optical module according to any one of claims 1 to 5, mounted on the substrate,
An amplifier circuit mounted on the same surface as the optical module, for amplifying and shaping an electrical signal output from the light receiving element;
A drive circuit that is mounted on the back surface of the surface on which the optical module is mounted, and that supplies an electrical signal to the light emitting element;
A transmission / reception circuit for optical communication, comprising: