JP2007266400A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module that can be assembled more efficiently with a smaller number of components, and that is highly reliable and less expensive. <P>SOLUTION: The optical module 1 comprises: an optical transmitter assembly for externally transmitting optical signals; an optical receiver assembly for receiving optical signals from the outside; and a circuit board for controlling the optical transmitter assembly and optical receiver assembly, wherein the optical transmitter assembly converts optical signals from the circuit board into optical signals for transmission to a transmission optical fiber through an optical connector, and the optical receiver assembly transmits optical signals from a reception optical fiber to the circuit board as electrical signal through the optical connector. An integrated optical adaptor 2 for connecting the optical connector which is attached to the transmission and reception optical fibers is packaged in a case 3 together with the optical transmitter assembly, optical receiver assembly, and circuit board. A transmission optical connector 41t located on the circuit side and a reception optical connector 41r located on the circuit side are connected to the optical adaptor 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical module that converts an electrical signal from a network device into an optical signal and transmits it to the outside, and converts an optical signal received from the outside into an electrical signal and transmits it to the network device.

  In recent years, the Internet has been established as a communication infrastructure, and various types of industries and services have been taken in regardless of the type of information such as data communication, voice, and video, and its application range continues to expand. In line with this, the line capacity is steadily increasing. Among them, Ethernet (registered trademark) is widely used as a core technology widely used in home LANs and WANs because of its low cost and simple operability.

  An optical module (for example, an optical transceiver) is used to transmit and receive an Ethernet signal. The optical module includes an optical transmission assembly that transmits an optical signal to the outside, an optical reception assembly that receives an optical signal from the outside, and a circuit board that controls the optical transmission assembly and the optical reception assembly. The electrical signal is converted into an optical signal by the optical transmission assembly, and the optical signal is transmitted to the transmission optical fiber through the optical connector. The optical signal from the reception optical fiber is transmitted to the circuit board by the optical reception assembly through the optical connector. It is transmitted as an electrical signal.

  As shown in FIG. 5, the conventional optical module 61 has transmission / reception optical fibers in the ferrule holding portions (receptacle portions) ft and fr of a receptacle type optical transmission assembly (TOSA) and optical reception assembly (ROSA) (not shown). The SC latch 62 that engages with the connected SC optical plug is fitted, and this is fitted to the optical connector 64 that is the end of the case (housing) 63 on the transmission / reception side. SC optical plugs are respectively inserted into the optical connector portions 64, and the SC optical plugs are fitted to the ferrule holding portions f.

  Further, an inner shield 65 for preventing electromagnetic waves from entering and exiting is fitted to the rear end (circuit side) of the ferrule holding part ft of the optical transmission assembly. The ferrule holding part fr of the optical receiving assembly is formed with a shield part for preventing electromagnetic waves from entering and exiting.

  The prior art document information related to the invention of this application includes the following.

Japanese Patent Laid-Open No. 2-180439 JP 7-244229 A

  As described above, the conventional optical modules often adopt the receptacle type as the optical transmission assembly and the optical reception assembly. However, this case has the following problems.

  1) The dimensional tolerance of the case 63 (in particular, the optical connector portion 64) is severe, and the additional processing cost is high. Therefore, the cost of the case 53 and the optical module increases.

  2) The structure of the ferrule holding portions ft and fr is complicated, and since this is manufactured by cutting, the processing cost is high.

  3) The number of necessary parts such as the SC latch 62 and the inner shield 65 is large, and it is difficult to manage the parts.

  4) Optical coupling fluctuation (connection loss) increases due to the wobbling of the optical transmitting assembly and the optical receiving assembly or wobbling of the optical connector (poor wiggle characteristics).

  5) Since there is a gap in the periphery of each ferrule holding part f and the inner shield 65 is fitted only to the ferrule holding part f of the optical transmission assembly, it is weak against EMI (electromagnetic interference). In addition, there is a gap between the optical transmission assembly and the case 63, and the inner shield 65 is necessary to be strong against EMI.

  Further, the conventional optical module 61 has a structure with a small degree of freedom in mounting place because the optical transmission assembly and the optical reception assembly are always arranged facing the optical connector portion 64.

  Accordingly, an object of the present invention is to provide an optical module that improves assembly workability, simplifies the number of parts, has high reliability, and is low in cost.

  The present invention has been devised to achieve the above object, and the invention of claim 1 includes an optical transmission assembly that transmits an optical signal to the outside, an optical reception assembly that receives an optical signal from the outside, and A circuit board that controls the optical transmission assembly and the optical reception assembly, and converts an electrical signal from the circuit board into an optical signal by the optical transmission assembly, and transmits the optical signal to the transmission optical fiber through the optical connector. In the optical module for transmitting an optical signal from the receiving optical fiber as an electric signal to the circuit board by the optical receiving assembly through the optical connector, an integrated light for connecting the optical connector attached to the transmitting / receiving optical fiber. An adapter is mounted on a case together with the optical transmitter assembly, the optical receiver assembly, and the circuit board. With connecting credit optical connector, an optical module connected to the receiving optical connector of the circuit side.

  The invention according to claim 2 is the optical module according to claim 1, wherein the case is provided with a shielding portion that electromagnetically shields the optical connector portion on which the optical adapter is mounted and the circuit portion on which the circuit board is housed.

  The invention according to claim 3 is the light according to claim 2, wherein the case is composed of a case divided into two upper and lower parts, and the shielding portion is composed of a lower case wall provided in the lower case and an upper case wall provided in the upper case. It is a module.

  According to a fourth aspect of the present invention, in the optical module according to any one of the first to third aspects, the circuit-side optical connector for transmission and the optical connector for reception on the circuit side are simple SC optical connectors.

  A fifth aspect of the present invention is the optical module according to any one of the first to fourth aspects, wherein the optical adapter is made of metal.

  A sixth aspect of the present invention is the optical module according to any one of the first to fourth aspects, wherein the optical adapter is made of a resin plated with metal.

  According to the present invention, by using a commercially available SC optical adapter, the number of parts can be reduced to one, the arrangement of the optical transceiver assembly can be freely designed, and the wiggle characteristics can be improved. Also, EMI characteristics can be improved without using an inner shield or the like.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  First, the overall configuration of the optical module according to the present embodiment (here, an example of an optical transceiver) will be described with reference to FIG.

  As shown in FIG. 3, the optical module 1 converts a plurality of electrical signals into wavelength-multiplexed optical signals and transmits them to a transmission optical fiber that is a transmission path, and wavelength-multiplexed light from a reception optical fiber that is a transmission path. This is for receiving a signal and converting it into an electric signal for transmission, and is also called a 4-wave WDM (Wideband Wavelength Division Multiplexing) LX4 optical transceiver.

  The optical module 1 includes a circuit board (main board) 33, an optical transmission assembly (TOSA) 34 mounted on the circuit board 33 via a spacer s having an integral structure, and an optical reception assembly (ROSA) 35. .

  The circuit board 33 is formed with four transmission lanes for transmitting electrical signals from network devices such as a switching hub and a media converter to which the optical module 1 is connected. The circuit board 33 is also formed with a receiving lane for transmitting an electrical signal from the optical receiving assembly 35.

  The other end (the opposite end to the SC optical connector side described later) of the circuit board 33 on the network device side is a card edge portion in which a plurality of terminals are formed, and is fitted to the card edge connector provided in the network device. Thus, the hot insertion and removal of the optical module 1 is possible.

  The optical transmission assembly 34 includes four 1310 nm band DFB-LDs that convert electrical signals from four transmission lanes into optical signals, and an optical multiplexer that wavelength-multiplexes the optical signals of the LDs. Are housed in a box-shaped OSA base 34b made of a metal such as Al having high heat dissipation. Each LD is one in which an LD element as a light emitting element is housed in a Can package.

  The wavelength of each LD is 1275, 1300, 1325, 1350 nm. As the optical multiplexer, four optical filters that reflect optical signals in a predetermined wavelength band and transmit optical signals in other wavelength bands are used.

  One end of a transmission pigtail fiber 40t that transmits a wavelength-multiplexed optical signal from the optical multiplexer is connected to the optical transmission assembly 34 via a simple SC optical connector. The other end of the transmission pigtail fiber 40t is connected to the transmission optical fiber 32t via an SC optical connector, which will be described later, and a transmission simple SC optical connector 41t as a circuit-side transmission optical connector.

  With this configuration, the optical output of the optical transmission assembly 34 can be transmitted in a free form using the transmission pigtail fiber 40t. Therefore, it is possible to greatly reduce the restriction on the place where the optical transmission assembly 34 is arranged in the optical module 1. The optical receiver assembly 35 is similar.

  The simple SC optical connector is compatible with SC optical connectors that are widely used in optical communication networks, and is used to connect optical modules such as ONU (Optical Network Unit) installed in the home, as well as for communication service company equipment. This is a low-cost optical connector suitable for optical cable termination racks such as FTM (Fiber Termination Module). When the SC optical plug is interconnected via an adapter, the SC optical plug and the optical adapter on one side are combined into a receptacle, so that the number of parts is 5 as compared with the optical adapter (13 parts) of a normal SC optical connector. Reduced to parts and realized significant economic effects.

  More specifically, the simple SC optical connector includes an optical plug and a simple optical adapter. The simple optical adapter includes five parts including a simple plug constituted by a boot and a simple ferrule, a split sleeve, and a simple receptacle constituted by a sleeve and a housing.

  The optical receiving assembly 35 is a 4ch-PD comprising an optical demultiplexer for demultiplexing a wavelength multiplexed optical signal from a receiving optical fiber, and four PDs (photodiodes) for converting the demultiplexed optical signal into an electrical signal. An array and four preamplifiers for amplifying each electrical signal are provided. As the optical demultiplexer, a four-layer dielectric multilayer filter is used.

  One end of a receiving pigtail fiber 40r is connected to the receiving optical fiber via an SC optical connector, which will be described later, and a simple receiving SC optical connector 41r as a circuit side receiving optical connector.

  The other end of the receiving pigtail fiber 40r is connected to the optical receiving assembly 35 via a simple SC optical connector.

  The dimensions of the optical module 1 are about 80 mm in total length, about 40 mm in width, and 50-60 mm in length of the circuit board 3.

  FIG. 1 is a perspective view of a main part of an optical module showing a preferred embodiment of the present invention, and FIG. 2 is a longitudinal sectional view showing a completed state thereof.

  As shown in FIGS. 1 and 2, an optical module 1 according to this embodiment includes a commercially available SC optical adapter 2 (shaded in FIGS. 1 and 2) as an integrated optical adapter for connecting optical fibers for transmission and reception. Part) is mounted on the case 3 together with the optical transmission assembly, the optical reception assembly, and the circuit board described above, and the SC optical adapter 2 is connected to the transmission simple optical connector 41t and to the reception simple optical connector 41r. It is what.

  The circuit board 33, the optical transmission assembly 34, the transmission pigtail fiber 40t, the reception pigtail fiber 40r, and the optical reception assembly 35 described with reference to FIG. And an upper case 3u having a substantially U-shaped cross section. The case 3 is formed of a metal having high heat dissipation such as Al, Mg alloy, Zn alloy. Among these, Mg alloy is inferior in heat dissipation characteristics compared with Al. Zn alloy is heavier than Al and is vulnerable to impact. Therefore, it is preferable to use Al that is light and has good heat dissipation characteristics. The part of the optical module 1 on the side of the network device that houses these components is a circuit unit 4.

  An end of the lower case 3d on the transmission / reception path side is a lower sleeve 5d, and an upper sleeve 5u (see FIG. 3) is attached on the lower sleeve 5d. On the lower case 3d, after the components are assembled, the upper case 3u is attached.

  The lower sleeve 5 d is formed with a concave adapter housing portion 6 for housing the SC optical adapter 2, and the SC optical adapter 2 is housed in the adapter housing portion 6. The SC optical adapter 2 is fitted on the transmission / reception path side with a duplex SC optical plug to which a transmission optical fiber 32t and a reception optical fiber 32r (see FIG. 4) are integrally connected. These duplex SC optical plug and SC optical adapter 2 constitute a duplex SC optical connector.

  On the network device side of the SC optical adapter 2, a transmission simple SC optical connector 41t connected to the other end of the transmission pigtail fiber 40t is inserted and fitted, and connected to one end of the reception pigtail fiber 40r. A simple SC optical connector for receiving 41r is inserted and fitted. The portion on the transmission / reception path side that houses the SC optical adapter 2 of the optical module 1 is an optical connector portion 7.

  In the lower case 3d, a lower case wall 8d for electromagnetically blocking the circuit portion 4 and the optical connector portion 7 at the boundary portion between the circuit portion 4 and the optical connector portion 7 blocks the transverse section of the lower case 3d. In this way, it is provided upright from the bottom surface of the lower case 3d.

  In the upper case 3u, an upper case wall 8u for electromagnetically blocking the circuit portion 4 and the optical connector portion 7 at the boundary portion between the circuit portion 4 and the optical connector portion 7 blocks the transverse section of the upper case 3u. Thus, the upper case 3u is provided so as to extend vertically downward from the inner upper surface.

  The lower case wall 8d and the upper case wall 8u constitute the shielding portion 8. In FIG. 2, the shielding portion 8 is shown as an example in which the tip on the transmission / reception path side of the upper case wall 8 u is formed in a substantially inverted L shape so as to be lower than the tip of the lower case wall 8 d.

  The SC optical adapter 2 may be made of a metal having high heat dissipation such as Al. The SC optical adapter 2 may be made of resin and then plated with metal.

  The operation of this embodiment will be described.

  The optical module 1 uses a commercially available integrated SC optical adapter 2 so that two SC optical plugs, to which transmission / reception optical fibers 32t and 32r are integrally connected, are collectively inserted from the transmission / reception path side. Simple SC optical connectors 41t and 41r to which tail fibers 40t and 40r are connected are respectively inserted from the circuit side.

  Thereby, the transmission pigtail fiber 40t and the transmission optical fiber 32t can be easily connected via the SC optical adapter 2. Similarly, the receiving optical fiber 32r and the receiving pigtail fiber 40r can be easily connected.

  Therefore, according to the optical module 1, the number of components of the optical connector portion 7 can be limited to only the SC optical adapter 2. The SC optical adapter 2 is provided at the end of the lower case 3d on the transmission / reception path side, and the optical I / F (interface) is a connector adapter connection made up of the SC optical plug and the SC optical adapter 2. Wiggle characteristics (optical coupling fluctuation (fluctuation in connection loss) due to wobbling of the optical connector) can be greatly improved compared to the prior art.

  That is, since the accuracy of optical coupling is borne by the SC optical adapter 2 manufactured with high accuracy, even if the SC optical adapter 2 moves in the case 3, the wiggle characteristic does not become a problem.

  Further, the optical connector portion 7 only needs to form the concave adapter housing portion 6 for housing the SC optical adapter 2 in the lower sleeve 5d, and the dimensional tolerance of the case portion can be loosened, so that additional processing or the like can be eliminated. it can.

  Furthermore, since the parts such as the ferrule holding part (receptacle part) f and the SC latch 62 as in the conventional optical module 61 of FIG. 6 are not required, the number of parts to be managed is reduced.

  Since the case 3 is provided with the shielding portion 8 that electromagnetically shields the circuit portion 4 and the optical connector portion 7, the optical connector portion 7 and the circuit portion 4 are completely shielded by the metal wall of the case 3, so that the EMI The characteristics are improved.

  That is, the optical module 1 can improve the EMI characteristics without using an inner shield or the like. This is a straight line along the length direction of the optical module 1 of the lower case wall 8d and the upper case wall 8u constituting the shielding portion 8 for electromagnetic shielding at the boundary portion between the circuit portion 4 and the optical connector portion 7. This is because the typical gap has become smaller.

  By providing the shielding portion 8 in the case 3, the inner shield 65 as in the conventional optical module 61 is not required, and the number of components to be managed is reduced in this respect as well.

  Therefore, according to the connection structure 1, it is possible to improve the assembling workability of the optical module 1, simplify the number of parts, provide a highly reliable and low-cost optical module.

  In addition, the simplified SC optical connectors 41t and 41r are used as the optical transmission / reception connectors on the circuit side, and the mounting space for the optical transmission / reception connector on the circuit side can be reduced by reducing the size of the optical transmission / reception connector on the circuit side. Circuit mounting space can be increased.

  Thereby, since the electromagnetic gap in the SC optical adapter 2 can be reduced, the EMI characteristics are improved.

  Since the SC optical adapter 2 is made of metal or a resin-plated metal, the SC optical adapter 2 becomes a second electromagnetic wall in addition to the shielding portion 8, and the EMI characteristics can be further improved. .

  Next, a modified example of the shielding portion 8 will be described with reference to FIGS. 4, 5 (a), and 5 (b).

  As shown in FIG. 4, the shielding part 41 is formed in a substantially inverted L shape so that the tip of the upper case wall 8u on the circuit side is lower than the tip of the lower case wall 8d. .

  Here, the width of the lower case wall 8d is L1, the width of the upper case wall 8u is L2, the vertical gap between the lower case wall 8d and the upper case wall 8u is L3, and the lower case wall 8d and the upper case wall are used. The gap between the front and rear of the wall 8u is L4, and the length of the upper case wall 8u that is below the tip of the lower case wall 8d is L5.

  The dimension of the shielding part 41 is 0.2 to 2 mm in the preferable dimension range of L1, the optimum value is 1 mm, the preferred dimension range of L2 is L1 <L2 <3 mm, the optimum value is 2 mm, and the preferred dimension range of L3 is 0 to 0.2 mm, the optimum value is 0 mm, the preferred dimension range of L4 is 0 to 0.2 mm, the optimum value is 0 mm, the preferred dimension range of L5 is L3 <L5 <1 mm, and the optimum value is 0.5 mm.

  Further, as a modification of the shielding portion 8, as shown in FIG. 5A, the tip of the upper case wall 8u on the transmission / reception path side and the circuit side is lower than the tip of the lower case wall 8d. As shown in FIG. 5B, a protrusion 41 may be provided at the tip of the lower case wall 8d so that the protrusion 41 contacts the upper case wall 8d. .

  In short, as shown in FIG. 5C, the upper case wall 8u and the lower case wall 8d are linear along the length direction of the optical module between the upper case wall 8u and the lower case wall 8d. Any shape may be used as long as no gap g is formed.

  In the above-described embodiment, the SC optical adapter 2 is used as the optical adapter, and the SC optical connector is connected to the SC optical adapter as the optical connector. However, the optical adapter is appropriately changed according to the optical connector, and this change is made. An optical module may be configured by connecting an FC optical connector or a plug-in optical connector to the optical adapter.

  In the above embodiment, the optical transmission assembly 34 including four LDs and the optical reception assembly 35 including four PDs have been described. However, the optical transmission assembly and the optical reception assembly include at least one LD, What is necessary is just to provide PD.

It is a perspective view of the principal part of the optical module which shows suitable embodiment of this invention. It is a longitudinal cross-sectional view which shows the completion state of the optical module shown in FIG. It is a perspective view which shows the internal structure of the optical module shown in FIG. It is a longitudinal cross-sectional view of the modification of the shielding part shown in FIG. 5 (a) and 5 (b) are longitudinal sectional views showing an example of the shielding portion, and FIG. 5 (c) is a longitudinal sectional view showing a conventional shielding portion. It is a perspective view of the conventional optical module.

Explanation of symbols

1 Optical Module 2 Optical Adapter 3d Lower Case 41t Simple SC Optical Connector for Transmission (Circuit-side Transmission Optical Connector)
41r Simple SC optical connector for reception (circuit side optical connector for reception)

Claims (6)

  An optical transmission assembly that transmits an optical signal to the outside; an optical reception assembly that receives an optical signal from the outside; and a circuit board that controls the optical transmission assembly and the optical reception assembly. The optical signal is converted into an optical signal by the optical transmission assembly, and the optical signal is transmitted to the transmission optical fiber through the optical connector. The optical signal from the reception optical fiber is transmitted to the circuit board by the optical reception assembly through the optical connector. In an optical module that transmits as an electrical signal, an integrated optical adapter that connects an optical connector attached to an optical fiber for transmission and reception is mounted on a case together with the optical transmission assembly, the optical reception assembly, and the circuit board, and the optical The optical connector for transmission on the circuit side is connected to the adapter, and the optical connector for reception on the circuit side is connected Light module according to claim.   The optical module according to claim 1, wherein the case is provided with a shielding portion that electromagnetically shields an optical connector portion on which the optical adapter is mounted and a circuit portion on which the circuit board is housed.   The optical module according to claim 2, wherein the case is composed of a case divided into upper and lower parts, and the shielding portion is composed of a lower case wall provided in the lower case and an upper case wall provided in the upper case.   The optical module according to claim 1, wherein the circuit-side transmission optical connector and the circuit-side reception optical connector are simple SC optical connectors.   The optical module according to claim 1, wherein the optical adapter is made of metal. The optical module according to claim 1, wherein the optical adapter is made of a resin plated with metal.

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