JP2013029640A - Optical transceiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transceiver capable of effectively reducing noise emission to the outside with a simple structure, without increasing a volume or dimension of the optical transceiver.SOLUTION: An optical transceiver 20 comprises: a receptacle member 8 for loading an optical connector; a base cover 9 where optical subassemblies 1a and 1b equipped with photoelectric conversion elements and a circuit substrate 2 with optical subassemblies mounted thereon are held; and a top cover 10. A noise reflection sheet 12 with multiple metal pieces arranged with predetermined pitches is provided on an inner surface of an aperture part of the receptacle member 8, and it reduces an electromagnetic noise emitted from the optical transceiver 20 to the outside through the receptacle member 8. The noise reflection sheet 12 can be provided also on inner surface of the base cover 9 or of the top cover 10.

Description

  The present invention relates to an optical transceiver used for data communication using an optical signal.

  An optical data link used for optical communication includes a transmitting optical sub-assembly (TOSA) for transmitting an optical signal, a receiving optical sub-assembly (ROSA) for receiving an optical signal, Alternatively, an optical subassembly such as a transmission / reception optical subassembly having both configurations for transmitting and receiving optical signals is housed and held in a metal casing together with a circuit board on which a large number of electronic components are mounted. In this case, what has both transmission and reception functions is generally called a pluggable optical transceiver (hereinafter referred to as an optical transceiver).

  FIG. 11 is a diagram illustrating an example of a conventional optical transceiver 100. For example, the optical transceiver 100 is formed in a rectangular shape in which a rear portion of the receptacle member 106 is surrounded by a metal casing 105 having a rectangular cross section. ing. The optical transceiver 100 is removably fitted into the cage 102 placed on the host substrate 104 through a panel opening 103a provided in the front panel 103 of the host device, and is disposed in the back of the cage 102. It is electrically connected by a connector (not shown). In addition, an optical connector 101 fitted with an optical fiber is inserted into the receptacle member 106 and optically connected to a light emitting element and a light receiving element mounted on the optical transceiver 100 to transmit / receive optical signals.

  In such an optical transceiver, in order to suppress electromagnetic radiation (EMI) from the inside to the outside of the host device and to promote heat dissipation, the metal casing 105 of the optical transceiver 100 is connected to a grounded cage 102 or Generally, electromagnetic shielding is performed by electrically contacting the opening 103a of the front panel of the host device.

  For example, in Patent Document 1, an elastic finger provided on a metal cover that covers an optical transceiver protrudes outward from the metal cover and is in electrical contact with the inner surface of the cage when the optical connector is inserted. When an EMI shield is formed and the optical connector is not inserted, an elastic finger is disclosed that is not in contact with the cage and facilitates the mounting and removal of the module. Patent Document 2 discloses an optical transmission / reception module provided with a metal shielding portion that closes a gap between an insertion port for inserting an optical fiber connector and a receptacle portion.

JP 2007-233261 A JP 2003-270492 A

  In general, optical transceivers that take EMI shielding into consideration are grounded by forming a plurality of electrical connection paths with a plurality of fingers (or tabs) between the front panel of the host device and the cage, and between the optical transceiver housing and the cage. Efforts have been made to stabilize the electric potential and to reduce the gap portion in the vicinity of the panel opening that serves as a leakage port to the outside, and various proposals have been made as disclosed in the above-mentioned patent documents.

  However, one of the causes of electromagnetic noise radiating from the optical transceiver to the outside is the presence of an opening for connecting the optical module (TOSA, ROSA) and the optical connector. This is because the opening through which the signal light is transmitted is physically closed by a lens or the like, but acts in the same way as the opening in terms of blocking electromagnetic noise. And by increasing the transmission speed, the main frequency and higher harmonic components are increased, and as a result, a frequency band equal to or higher than the cutoff frequency of the opening shape has been used.

  Therefore, the problem of electromagnetic noise radiated from the inside of the optical transceiver (or inside the network device) to the outside through the opening has been increasing. The opening is an opening having a size determined by an industry standard, and any optical transceiver having the same type has the same opening size.

  In order to suppress electromagnetic noise from this opening, for example, it is known to add an adapter containing an electromagnetic noise absorbing filler to this opening to reduce the emission of electromagnetic noise from the inside of the optical transceiver. However, when a new adapter containing an electromagnetic absorber is provided, the number of parts is increased and it is not suitable for miniaturization.

  The present invention has been made in view of these circumstances, and provides an optical transceiver capable of effectively reducing noise radiation to the outside with a simple structure without increasing the volume and size of the optical transceiver. With the goal.

  An optical transceiver according to the present invention is an optical transceiver having a housing for housing an optical subassembly on which a photoelectric conversion element is mounted and a circuit board on which the optical subassembly is mounted and for connecting an optical connector. In addition, a noise reflection sheet in which a plurality of metal pieces are arranged at a predetermined pitch is provided.

  The noise reflection sheet is provided on the optical connector connection part (receptacle member), base cover, top cover, etc. that form the housing. When the noise reflection sheet is provided on the optical connector connection part, noise is generated at the tip of the opening of the optical connector connection part. A stopper that contacts the reflection sheet is provided. The pitch of the plurality of metal pieces is less than ¼ of the wavelength of the electromagnetic noise that is the object of radiation suppression, and this pitch may be continuously changed.

  According to the present invention, noise emission from the optical transceiver to the outside can be effectively reduced with a simple structure without increasing the volume and size of the optical transceiver. Moreover, when a noise reflection sheet is provided in the optical connector connection portion, noise radiated to the outside through the optical connector can be suppressed. Furthermore, by adjusting the shape and pitch of the metal piece, the frequency and frequency range of the target electromagnetic noise can be easily adjusted, and radiation from the inside of the optical transceiver can be suppressed over a wide band. For this reason, it can be made smaller and thinner than a radio wave absorber.

It is a perspective view which shows the state which opened the top cover as an example of the optical transceiver which concerns on this invention. It is a perspective view showing an example of an optical transceiver concerning the present invention. It is a perspective view of the optical connector connection part of the optical transceiver which concerns on this invention. It is a figure which shows the assembly body of a noise reflection sheet. It is a figure which shows an example of a noise reflection sheet. It is a figure which shows the cross section of a noise reflection sheet. It is a figure which shows the other example of a noise reflection sheet. It is a figure for demonstrating the simulation regarding the optical transceiver of this invention. It is a figure which shows the simulation result regarding the optical transceiver in this invention. It is a figure which shows an example of the top cover of the optical transceiver which concerns on this invention. It is a figure which shows the state which mounted | wore the host device with the optical transceiver connected to the optical connector.

Hereinafter, preferred embodiments of the optical transceiver of the present invention will be described with reference to the drawings.
First, in the optical transceiver of the present invention, an example in which a noise reflecting sheet is provided on a receptacle member that is an optical connector connecting portion will be described. FIG. 1 is a perspective view of an example of an optical transceiver according to the present invention, illustrating a state in which a top cover is opened, and FIG. 2 is a diagram illustrating a state in which the top cover is closed. FIG. 3 is a perspective view of the optical connector connecting portion (receptacle member) in the optical transceiver shown in FIGS.

  In the figure, 1a is TOSA, 1b is ROSA, 2 is a first circuit board, 3 is a second circuit board, 4 and 5 are flexible boards (FPC), 6 is a board holder, 7 is a metal holding member, 8 is a receptacle member corresponding to the optical connector connecting portion of the present invention, 9 is a base cover, 10 is a top cover, 11 is a stopper, 12 is a noise reflecting sheet, and 13 is a ground shield member. Here, the receptacle member 8, the base cover 9, and the top cover 10 constitute a housing of the optical transceiver of the present invention.

  The TOSA 1a that is an optical subassembly that transmits an optical signal and the ROSA 1b that is an optical subassembly that receives an optical signal are arranged in a parallel state in the width direction (X-axis direction) and assembled together by the receptacle member 8 to form a subassembly. A unit. A light emitting element and a light receiving element, which are photoelectric conversion elements, are mounted on these TOSA 1a and ROSA 1b, respectively.

  Electrical signal processing, control, and the like for the TOSA 1a and the ROSA 1b are performed by an electronic circuit including a group of electronic circuit components mounted on the first circuit board 2 and the second circuit board 3. The TOSA 1a and the ROSA 1b are electrically connected to the first circuit board 2 via the flexible board 5 (FPC). The first circuit board 2 and the second circuit board 3 are assembled and arranged in the vertical direction (Y-axis direction) by the board holder 6 and are electrically connected via the flexible board 4 (FPC). .

  For example, the first circuit board 2 can be used as a main circuit board for a circuit device that performs main control of an optical transceiver, and can be a board on which a heat-generating component such as an IC circuit is mounted. Further, the second circuit board 3 can be a board on which a control circuit and electronic components that cannot be accommodated only by the first circuit board 2 are mounted by adding an additional function. However, this does not mean that any control circuit / electronic component must be mounted on the first and second circuit boards, and the second circuit board 3 need not be provided if it can be accommodated by one circuit board. A connector portion 2a for electrically connecting the optical transceiver to the host device is provided behind the first circuit board 2.

  The holding member 7 is made of metal, for example, a front shield portion that has a fitting hole that is fitted to the front portion (Z-axis direction) of the TOSA 1a and ROSA 1b and shields electromagnetic waves from the gap portion on the front end side, and the TOSA 1a, It has a U-shaped gripping part that grips the main body part of the ROSA 1b from above and below.

  A receptacle member 8 for inserting an optical connector (not shown) is coupled to the front portion of the base cover 9. The receptacle member 8 is formed by molding an insulating resin or metal, has a socket hole 8a that is a pair of openings into which an optical connector is inserted and attached, and communicates with the sleeve portions of the TOSA 1a and ROSA 1b.

  The base cover 9 is formed of a metal material having heat dissipation and shielding functions, and includes a bottom wall and a pair of side walls. In the base cover 9, the front shield portion of the holding member 7 is accommodated in contact with the inner end of the receptacle member 8, and the first circuit board 2 and the second circuit board 3 are positioned together with the board holder 6. Are stored. Further, a locking portion 9 a that locks one end portion 10 a of the top cover 10 so as to be rotatable is provided at the rear end of the side wall of the base cover 9.

  The top cover 10 has a lid shape that closes the opening at the top of the base cover 9, and can be formed of a metal material having a heat dissipation and shielding function, like the base cover 9. A holding portion for holding and fixing the TOSA 1a and ROSA 1b from above is provided on the inner surface on the front side of the top cover 10, and the TOSA 1a and ROSA 1b are held and fixed when the top cover 10 is closed. It is like that.

  The ground shield member 13 shown in FIG. 2 is formed from a metal plate having elasticity. When the optical transceiver is inserted into the cage 20 of the host device, the ground shield member 13 is for grounding the ground by bringing the casing into electrical contact with the inner surface of the cage 20 and providing a shielding function to the metal casing. It is.

  As described above, the optical transceiver has an internal space extending in the Z-axis direction, and includes a housing including at least an inner surface of the base cover 9 and the top cover 10 made of metal. For this reason, the internal space of the housing has the same structure as the waveguide extending in the Z-axis direction. Therefore, noise having a frequency equal to or higher than the cutoff frequency determined by the dimensions of the internal space propagates in the Z-axis direction through the internal space of the housing.

  For this reason, in this embodiment, in order to suppress electromagnetic noise radiated to the outside from the receptacle member 8 side, the bottom surface and both side surfaces of the socket hole 8a, which is a pair of openings into which the optical connector of the receptacle member 8 is mounted. The noise reflection sheet 12 having a plurality of metal pieces at a predetermined pitch is provided on a surface along the direction in which electromagnetic noise is radiated. The noise reflection sheet will be described in detail later, and a high impedance surface (electromagnetic radiation noise reflection surface) is formed for electromagnetic noise of a specific frequency.

  In addition, by providing a stopper 11 at the tip of the socket hole 8a, when the noise reflecting sheet 12 is inserted by sliding from the TOSA 1a or SOSA 1b side (the optical module side indicated by the arrow in FIG. 3), the stopper 11 Abutting on the end of the noise reflection sheet 12 prevents the noise reflection sheet 12 from being positioned and dropped off. The stopper 11 may be formed separately from the receptacle member 8 and may be fixed to the receptacle member 8 or may be molded integrally with the receptacle member 8.

  As shown in FIG. 4, the noise reflection sheet 12 mounted in the opening of the receptacle member 8 is configured as an assembly having three surfaces with a U-shaped cross section, and is inserted into the opening of the receptacle member 8 from the optical module side. And fixed. At that time, for example, it is desirable to provide a guide groove or the like on the inner surface of the opening of the receptacle member 8 so that the noise reflecting sheet 12 on the side surface of the assembly of the noise reflecting sheet 12 does not fall down.

  The assembly of the noise reflecting sheet 12 shown in FIG. 4 is configured by assembling the noise reflecting sheet 12 having each surface individually manufactured, for example, as shown in FIG. 5 (A), or FIG. 5 (B). As shown in FIG. 5, the three surfaces integrally formed can be bent. In the present embodiment, the noise reflecting sheet 12 is provided on the three surfaces in the opening of the receptacle member 8, but noise radiation to the outside can be reduced if provided on at least one surface.

FIG. 6 is a cross-sectional view of the noise reflecting sheet, and the noise reflecting sheet of the present invention will be described.
For example, as shown in FIG. 6 (A), the noise reflecting sheet 12 has a pitch p that is less than a quarter of the wavelength of the electromagnetic noise to be cut off on the surface along the direction in which the electromagnetic noise of the insulating sheet 15 radiates. A plurality of first-layer metal pieces 13a are provided. Here, the material of the metal piece 8a may be a metal material having excellent conductivity, and for example, a copper foil or the like can be used. Moreover, when manufacturing the noise reflection sheet 12, a general process for forming wiring on a printed circuit board can be used. For example, the insulating sheet 15 can be made using a glass / epoxy material, polyimide, ceramic, or the like as a base material. Alternatively, it may be created as a resin molding step in which the metal piece is filled with resin.

  Although the metal piece 13a of the noise reflecting sheet 12 shown in FIG. 6A is one layer, it may be composed of two layers. The noise reflection sheet 12 shown in FIG. 6B is a noise reflection sheet in the case where the metal piece has two layers, and the first-layer metal piece 13a and the second-layer metal piece 13b are connected to the connecting portion 14. The efficiency of noise reflection can be increased by connecting with. Note that the metal pieces 13b on the second layer surface may be electrically connected to each other. For example, as shown in FIG. 6C, the metal pieces 8b on the second layer are electrically connected to each other. You may comprise as a piece of metal. Here, when the noise reflecting sheet 12 shown in FIG. 6C is used, it is necessary to dispose the first-layer metal piece 13a so as to be located inside the opening.

  However, at least the arrangement pitch p of the metal pieces 13a of the first layer needs to be arranged at less than ¼ of the wavelength of electromagnetic noise to be subjected to radiation suppression. For example, when the optical module is used at a transmission rate of 25 Gbps, the fundamental wave is approximately 12.5 GHz / s. At this time, in order to suppress the second harmonic noise, the metal pieces 8a may be arranged with the arrangement pitch p of the metal pieces 8a of the first layer being 3.0 mm.

  FIG. 7 is a diagram illustrating still another example of the noise reflecting sheet. When the wavelength of the electromagnetic noise has a specific frequency band, as shown in FIG. 7, the pitch p of the arrangement of the first-layer metal pieces 13a is not fixed, but p1> p2> p3> ...> It is continuously changed so that pn. Here, the pitch p1 is set to be less than 1/4 with respect to the wavelength of the electromagnetic noise to be suppressed. Thereby, even when the electromagnetic noise to be suppressed is broadband noise including harmonics, noise emission can be effectively reduced. In the electromagnetic noise reflector 7 shown in FIG. 7, since the arrangement pitch p of the first-layer metal pieces 8a is sequentially changed, the shapes of the metal pieces 8a1 to 8a6 themselves are also sequentially different. . Further, in the electromagnetic noise reflector 7 shown in FIG. 7, the second-layer metal piece 8b may be provided, and the second-layer metal piece 8b may be integrally formed.

  In the present invention, the relationship between the arrangement pitch p of the first-layer metal pieces 13a and the noise wavelength to be suppressed is as described above, but the shape of the first-layer metal pieces 13a has a desired frequency. Various shapes can be selected to reflect and block noise from radiating out. For example, the shape of the metal piece 13a in the first layer can be various shapes such as a polygon such as a triangle or a quadrangle, a circle, an ellipse, or a spiral (spiral) shape. You may select according to the shape of a housing.

  Next, a simulation performed to confirm the effect of the optical transceiver of the present invention will be described. FIG. 8 is a diagram for explaining a simulation related to the optical transceiver of the present invention, and FIG. 9 is a diagram showing a simulation result. As shown in FIG. 8, when the optical transceiver 20 side is the port 1 and the fiber boot side of the optical connector 30 is the port 2, a simulation of electromagnetic waves propagating from the port 1 to the port 2 was performed.

  In the simulation, as shown in FIG. 6C, the noise reflecting sheet 12 in which the second metal piece 13b is provided to the first metal piece 13a and the second metal piece 13b is integrated. Was arranged on three surfaces in the opening of the receptacle member 8. The pitch of the metal pieces 13a in the first layer was 3.2 mm. The simulation was performed for the case where the electromagnetic noise reflector 7 was not provided in the receptacle member 8 and the case where it was provided.

  FIG. 9 is a diagram showing the simulation results. The horizontal axis represents the frequency, and the vertical axis represents the electromagnetic wave propagating from port 1 to port 2 in the case where the optical noise reflector 7 is not provided in the optical connector 10 and the electromagnetic noise reflector 7. This is shown by a graph in which differences are provided. Depending on the presence or absence of the noise reflecting sheet 12 that forms the high impedance surface of the present invention, it can be confirmed that a large negative value is generally obtained in the vicinity of 12.6 GHz to 16.5 GHz. This means that when there is a high-impedance surface, the propagation of electromagnetic waves is suppressed near 13 GHz to 16 GHz compared to when there is no high-impedance surface, and electromagnetic noise that escapes from port 1 to port 2 is effective. It shows that it is suppressed to.

The example in which the noise reflecting sheet 12 is disposed on the inner surface of the opening of the receptacle member 8 constituting the housing has been described as the optical transceiver of the present invention. However, the noise reflecting sheet 12 is provided in the housing other than the receptacle member. Also good.
For example, as shown in FIG. 10, the noise reflection sheet 12 can be disposed on the inner surface of the top cover 10 of the optical transceiver 20. In this case, the metal pieces of the noise reflecting sheet 12 are arranged at a pitch less than ¼ of the wavelength of the electromagnetic noise to be radiation-suppressed along the longitudinal direction in which the optical transceiver 20 forms the waveguide. . Thereby, the noise reflection sheet 12 becomes a high impedance surface with respect to a specific wavelength, and radiation of electromagnetic noise to the outside can be reduced. In the example shown in FIG. 10, the arrangement of the metal pieces of the noise reflecting sheet 12 is three rows along the longitudinal direction, but may be constituted by one row. Further, the same effect can be obtained if the noise reflection sheet 12 is provided on the inner surface of the base cover 9 in addition to the inner surface of the top cover 10.

DESCRIPTION OF SYMBOLS 1a ... TOSA, 1b ... ROSA, 2 ... 1st circuit board, 3 ... 2nd circuit board, 4,5 ... flexible substrate, 6 ... substrate holder, 7 ... holding member, 8 ... receptacle member, 9 ... base cover DESCRIPTION OF SYMBOLS 10 ... Top cover, 11 ... Stopper, 12 ... Noise reflection sheet, 13 ... Metal piece, 14 ... Connection part, 15 ... Insulation sheet, 16 ... Ground shield member, 20, 100 ... Optical transceiver, 30, 101 ... Optical connector , 102 ... cage, 103 ... front panel, 104 ... host substrate, 105 ... housing.

Claims (6)

  An optical transceiver having an optical subassembly on which a photoelectric conversion element is mounted and a circuit board on which the optical subassembly is mounted, and having a housing for connecting an optical connector, wherein a plurality of metal pieces are disposed inside the housing. An optical transceiver characterized in that a noise reflection sheet is arranged with a predetermined pitch.   The housing includes an optical connector connecting portion for connecting an optical connector, and the noise reflecting sheet is provided on an inner surface of an opening of the optical connector connecting portion into which the optical connector is inserted. Item 4. The optical transceiver according to Item 1.   The optical transceiver according to claim 2, wherein a stopper that abuts on an end portion of the noise reflecting sheet is provided at a front end portion of an inner surface of the opening portion of the optical connector connection portion.   The housing has a base cover and a top cover that house the optical subassembly and the circuit board, and the noise reflecting sheet is provided on the inner surface of the base cover and / or the inner surface of the top cover. The optical transceiver according to any one of claims 1 to 3.   5. The optical transceiver according to claim 1, wherein a pitch of the plurality of metal pieces is less than ¼ of a wavelength of electromagnetic noise to be radiation-suppressed.   The optical transceiver according to any one of claims 1 to 5, wherein a pitch of the plurality of metal pieces is continuously changed.

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