JP5205853B2 - Single fiber bidirectional optical module - Google Patents

Description

  The present invention relates to a single-fiber bidirectional optical module that transmits and receives optical signals using a single optical fiber that facilitates mounting on a circuit board and reduces electrical crosstalk of signals from a transmission side to a reception side. .

  In recent years, the demand for single-fiber bidirectional communication that transmits and receives upstream and downstream signals using a single optical fiber has been rapidly expanding, centering on optical access systems. The transmission speed required for a single-fiber bidirectional optical module that transmits and receives an optical signal by this single-fiber bidirectional communication is high. For example, when used in a GE-PON (Gigabit Ethernet-Passive Optical Network), it is a gigabit class. In order to transmit and receive optical signals multiplexed with two or more wavelengths accurately at the high transmission speed as described above (that is, to enable high-quality transmission), electrical crosstalk from the transmitter to the receiver Need to be reduced.

For example, Patent Document 1 discloses a technique for reducing electrical crosstalk from an optical signal transmission unit of a single-fiber bidirectional optical module. As shown in FIG. 7, the single-fiber bidirectional optical module described in Patent Document 1 holds an optical signal transmitter 11 and an optical signal receiver 12 in a metal casing 13. In this single-fiber bidirectional optical module, the lead pins 11a of the optical signal transmitter 11 and the conductive pattern 22 of the circuit board 20 are solder-connected, and as shown in FIGS. 7A and 7B, the circuit board A pair of metal members 90 fixed to 20 are sandwiched from both the front and back sides of the circuit board 20 and attached to the circuit board 20. In this single fiber bidirectional optical module, a metal member 90 used for mounting on the circuit board 20 covers a part of the casing (the part holding the optical signal transmission unit), and the metal member 90 is grounded (GND). The electrical crosstalk is reduced by being electrically connected to ().
JP 2006-126495 A

  As in the technique disclosed in Patent Document 1 shown in FIG. 7, the housing 13 around the optical signal transmission unit 11 that is a noise source is sandwiched / fixed by a metal member 90 that is electrically connected to the GND. By strengthening the GND, a certain effect is recognized for the electrical crosstalk of the signal from the optical signal transmitter 11 to the optical signal receiver 12. However, according to the electromagnetic noise analysis conducted by the inventor, the potential of the housing 13 is microscopically affected by noise propagated through the air as it moves away from the metal member 90 connected to the GND. The GND potential is unstable due to the influence of noise propagating through the housing 13, and there is room for further improvement from the viewpoint of reducing electrical crosstalk. Moreover, in patent document 1, it attaches to the circuit board 20 on both sides of the circuit board 20 from the front and back of the circuit board 20 by the metal member 90 which covers the optical signal transmission part 11 of the single fiber bidirectional optical module 100. There is room for improvement in the mounting structure using time and effort.

  The present invention has been made in view of the above circumstances, and is a single-fiber bidirectional optical module that reduces electrical crosstalk of signals from a transmission unit to a reception unit and facilitates attachment to a circuit board. The purpose is to provide.

  The single-fiber bidirectional optical module according to the present invention includes a transmitter that transmits a first optical signal disposed along a first axis, and a second that is disposed along a second axis that intersects the first axis. A first optical filter disposed at the intersection of the first axis and the second axis, and via an optical fiber disposed on the first axis. A common conductor that transmits a first optical signal and receives a second optical signal, and that can be attached from one side of a circuit board to a housing portion that holds each of a transmitter, a receiver, and an optical fiber. It is characterized by being covered with a metal member and grounded.

The single-fiber bidirectional optical module includes a receiving unit that receives a third optical signal arranged along a third axis that intersects the first axis, and intersects the first axis and the third axis. A second optical filter may be arranged in the part, and the third optical signal may be received via the optical fiber.
In addition, it is preferable that a conductive metal member has an opening for joining with the said housing | casing part by welding. In addition, the conductive metal member is preferably composed of two members each having a substantially cylindrical shape divided in half, and is preferably attached by sandwiching the casing portion between the two members.

  According to the present invention, the single-fiber bidirectional optical module can be easily attached to the circuit board, and electrical crosstalk of signals from the transmission unit to the reception unit in a device (for example, an optical transceiver) including the module can be reduced. Can be reduced. Therefore, it is possible to reduce the manufacturing cost of a device including a single-fiber bidirectional optical module, and it is possible to obtain good reception sensitivity characteristics and a CN ratio in the receiving unit of the module.

  1 and 2 are diagrams for explaining a single-fiber bidirectional optical module (hereinafter referred to as an optical transceiver module) according to an embodiment of the present invention. FIG. 1A is a perspective view of the optical transceiver module. 1 (B) is a plan view thereof. FIG. 2A is a diagram showing the state where the optical transceiver module is attached to the circuit board, with the conductive metal member omitted, and FIG. 2B shows the optical coupling in the optical transceiver module. It is a schematic diagram explaining the mode of.

  As shown in FIG. 1, the optical transceiver module 1 according to the present invention includes a conductive metal member (hereinafter referred to as a metal member) 30 fixed to a circuit board 20 (see FIG. 2) attached to an optical transceiver module body 10. . The optical transceiver module main body 10 is the same as the optical transceiver module of FIG. 7, and is, for example, a diplexer type optical transceiver module that transmits and receives digital optical signals using a single optical fiber. The optical transceiver module 1 with the metal member 30 attached to the optical transceiver module main body 10 can be attached to the circuit board 20 by fixing the metal member 30 to the circuit board 20.

First, the optical transceiver module body 10 (hereinafter referred to as the module body 10) and the circuit board 20 will be described with reference to FIG.
The module body 10 includes an optical signal transmitter 11, an optical signal receiver 12, a housing 13, an optical transmission component 14, and the like.

  As shown in FIGS. 2 (A) and 2 (B), the optical signal transmission unit 11 and the optical signal reception unit 12 include stems 11b and 12b in which a plurality of lead pins 11a and 12a are attached by glass sealing, The condensing lenses 11c and 12c have a coaxial package including caps 11d and 12d fixed with sealing glass. On the stems 11b and 12b, mounting components such as a semiconductor light emitting element and a semiconductor light receiving element described later are mounted, and these are sealed by the package. The stems 11b and 12b are made of, for example, cold-rolled steel (SPCE steel) or Kovar material partially plated with gold, and the caps 11d and 12d are made of, for example, stainless steel with good machinability. It is a processed material. The mounting parts are sealed by sealing and welding the stems 11b and 12b and the caps 11d and 12d.

  As shown in FIG. 2B, the optical signal transmitter 11 is equipped with a semiconductor light emitting element (LD: Laser Diode) 11e that emits an optical signal of the first wavelength, and is emitted from the LD 11e. The optical signal passes through a WDM filter 13a (described later) included in the condensing lens 11c and the housing 13, and is transmitted to the outside through the optical fiber 14a in the optical transmission component 14. The LD 11e is electrically connected to some of the lead pins 11a among the plurality of lead pins 11a, and receives an electrical transmission signal from the outside of the optical signal transmitter 11 via the lead pin 11a.

  The optical signal receiver 12 is equipped with a semiconductor light receiving element (PD: Photo Diode) 12e. The PD 12e receives an optical signal incident from the optical fiber 14a in the optical transmission component 14 and reflected by the WDM filter 13a. The light is received through a cut filter 13b (described later) of the housing 13 and a condensing lens 12c. The optical signal propagating through the optical fiber 14a received by the PD 12e has a wavelength (second wavelength) different from that of the optical signal output from the optical signal transmitter 11. Preferably, the optical signal receiving unit 12 is equipped with a transimpedance amplifier (TIA) (not shown) that amplifies a weak electric signal generated by the PD 12e.

  When the TIA is mounted, the PD 12e and the TIA are electrically connected, and the TIA is electrically connected to some of the lead pins 12a among the plurality of lead pins 12a. The signal received by the PD 12e and converted into an electrical signal is amplified by the TIA, and the amplified electrical signal is sent out of the optical signal receiving unit 12 through the lead pin 12a. As the PD 12e, for example, an avalanche photodiode or a PIN photodiode can be used.

  The optical transmission component 14 is a component including, for example, an optical fiber 14a, a ferrule 14b, and a sleeve 14c. The optical fiber 14a is held by the ferrule 14b, and the ferrule 14b is held by the sleeve 14c. The ferrule 14b is provided at the end of the optical transmission component 14, and the end face of the optical fiber 14a is exposed at the end face thereof. In the optical transceiver module 1, the optical transmission component 14 emits signal light from the outside from the end face toward the optical signal transmission unit 11. This optical signal having the second wavelength is reflected by the WDM filter 13 a and received by the PD 12 e of the optical signal receiving unit 12. Further, the optical transmission component 14 transmits the signal light from the LD 11e received on its end face to the outside.

The following WDM filter 13a and cut filter 13b are also attached to the casing 13 to which the optical signal transmitter 11, the optical signal receiver 12, and the optical transmission component 14 as described above are attached.
The WDM filter 13a is a wavelength selection filter that selectively transmits or reflects light based on the wavelength of light, transmits the optical signal emitted from the optical signal transmission unit 11, and from one end of the optical fiber 14a. The optical signal is reflected and guided to the optical signal receiving unit 12.
The cut filter 13b transmits light of a specific wavelength and blocks light of other wavelengths, and the cut filter 13b allows an optical signal from the optical signal transmission unit 11 to be transmitted to the optical signal reception unit 12. Can be prevented.

  The casing 13 to which the above-described components are attached is made of a material capable of YAG laser welding, for example, a stainless steel material, and its basic shape is a cylindrical shape. The housing 13 is formed with an optical path hole 13c having a cylindrical axis as a central axis, and the optical path hole 13c has a WDM filter fixing portion 13d to which the WDM filter 13a is fixed. Moreover, the housing | casing 13 has the cut filter fixing hole 13e to which the cut filter 13b is fixed.

  Further, the housing 13 includes an optical signal transmitter fixing hole 13f, an optical signal receiver fixing surface 13g, and an optical transmission in which the optical signal transmitter 11, the optical signal receiver 12, and the optical transmission component 14 are aligned and fixed. It has a component fixing surface 13h. The optical signal transmission unit 11 is attached to the optical signal transmission unit fixing hole 13f by YAG welding the cap 11d of the optical signal transmission unit 11 to the optical signal transmission unit fixing wall 13i. The optical signal receiving unit 12 is attached to the optical signal receiving unit fixing surface 13g by YAG welding the end surface of the cap 12d of the optical signal receiving unit 12 to the cap fixing plane, and light to the optical transmission component fixing surface 13h. The transmission component 14 is attached by YAG welding the end surface of the sleeve 14c to the sleeve fixing plane.

  With this housing 13, the optical signal transmitter 11, the optical signal receiver 12, and the optical transmission component 14 allow the optical signal emitted from the LD 11e of the optical signal transmitter 11 to enter the optical fiber 14a through the WDM filter 13a. Then, alignment is performed such that the optical signal transmitted to the outside and emitted from the outside through the optical fiber 14a is reflected by the WDM filter 13a and enters the PD 12e of the optical signal receiving unit 12.

  That is, the optical signal transmission unit 11 that emits the optical signal having the first wavelength by the housing 13 is disposed along the first axis (the central axis of the housing 13) A, and the optical signal having the second wavelength. Is arranged along a second axis B that intersects the first axis. Further, in the optical filter (WDM filter 13a) that transmits light of the first wavelength and reflects light of the second wavelength by the housing 13, the first axis A and the second axis B intersect. Placed in position. Furthermore, the optical fiber 14a held by the optical fiber holding portion (ferrule 14b) along the first axis A is arranged at a predetermined position by the casing 13. That is, the light having the first wavelength emitted from the optical signal transmitter 11 is coupled to the optical fiber 14a after passing through the optical filter, and the light having the second wavelength propagated through the optical fiber 14a is the optical filter. Is disposed at a position where it is reflected by and coupled to the optical signal receiver 12.

  The circuit board 20 is used to exchange electrical signals with the optical signal transmission unit 11 and with the optical signal reception unit 12, and as shown in FIG. IC21 etc. which perform the transmission processing of the electrical signal etc. which are carried are mounted. A plurality of conductive patterns 22 for electrical connection with the module body 10 are formed on the circuit board 20.

  By attaching a metal member 30 (see FIG. 1), which will be described later, to the module body 10 as described above, the optical transceiver module 1 is obtained. The module main body 10 and the metal member 30 are attached by, for example, YAG welding. The optical transceiver module 1 is attached to the circuit board 20 by, for example, connecting the metal member 30 to the circuit board 20 by soldering and connecting the lead pins 11a and 12a and the conductive pattern 22 of the circuit board 20 by soldering. This can be done from one side of the substrate 20.

  Next, returning to FIG. 1, the metal member 30 according to the main part of the present invention will be described. The metal member 30 is attached to the module body 10 to reduce electrical crosstalk from the optical signal transmitter 11 of the optical transceiver module 1 and to attach the optical transceiver module 1 from one side of the circuit board 20. is there. The metal member 30 collectively covers a housing (housing portion) 13 that holds each of the optical signal transmitter 11, the optical signal receiver 12, and the optical transmission component 14 of the optical transceiver module 1, and the circuit board 20. Are electrically connected to a signal ground (SG). The metal member 30 can be attached to the circuit board by an operation only from one side of the circuit board 20. The metal member 30 includes a main body portion 31 and an attachment portion 32.

  As shown in FIG. 1A, the main body 31 of the metal member 30 includes at least an optical signal transmission unit 11 of the module main body 10 and a housing 13 continuing from the optical signal transmission unit 11 to the optical signal reception unit 12. Is a part covering the module body 10 from one side. In the example of FIG. 1A, the main body 31 further covers a sleeve 14c (see FIG. 2) of the optical transmission component 14.

  Further, as shown in FIG. 1B, the main body 31 has a notch 31a formed on the optical signal receiving unit 12 side. By forming the notch 31a in this way, when the metal member 30 is attached, it is possible to prevent the optical signal receiving unit 12 of the module body 10 from hindering the attachment. This notch 31a is used by the metal member 30 to receive the optical signal when the metal member 30 is attached to the circuit board 20, regardless of the position of the optical signal receiving unit 12 in the module body 10 for alignment. It is provided so as not to contact the part 12.

The main body 31 is formed so that the inner peripheral surface thereof is along the outer peripheral surface of the module main body 10. For example, the main body 31 has a shape corresponding to the casing 13 of the module main body 10 formed in a cylindrical shape, that is, half It has a cylindrical shape.
Moreover, in order to attach the metal member 30 to the module main body 10 and to electrically connect them, it is preferable to YAG weld the main body portion 31 of the metal member 30 and the module main body 10. Therefore, an opening 31 b is provided in a part of the main body portion 31 of the metal member 30 that is in contact with the housing 13 of the module main body 10. If the opening 31b is provided in this way, the welding trace can be confirmed when the edge and the housing 13 are YAG welded.

  The attachment part 32 of the metal member 30 is a part for attaching (fixing) the metal member 30 to the circuit board 20 and extends in a direction orthogonal to the direction in which the main body part 31 extends. The attachment portion 32 is soldered to the circuit board 20 and is preferably electrically connected to the signal ground of the circuit board 20.

  The metal member 30 having the main body portion 31 and the attachment portion 32 is made of, for example, a material capable of YAG laser welding (such as a stainless steel material). Further, the metal member 30 is attached to the module body 10 by YAG laser welding so that the front and rear (front and rear in the fiber axis direction) of the optical signal receiving unit 12 are sandwiched between the two mounting portions 32. Of the metal member 30 made of a stainless steel material, at least a portion to be soldered is subjected to a surface treatment with a material having good wettability such as gold plating, silver plating, or solder plating.

In the optical transceiver module 1 according to the present embodiment, by providing such a metal member 30, the strength of the electric field emitted from the module body 10 can be reduced. This has been confirmed by the inventors' tests.
In the test, the optical transceiver module 1 having the configuration of the present embodiment (the metal member 30 is attached to the module body 10 by YAG laser welding, and the metal member 30 is electrically connected to the SG of the circuit board 20 to be connected to the circuit board 20. Sample X1 was attached). A sample X2 having the same configuration as the sample X1 except that the metal member 30 is not provided (the housing 13 and the SG are not electrically connected) is prepared, and the technique disclosed in Patent Document 1 is disclosed. The configuration used was prepared as X3. And about these samples X1, X2, and X3, the intensity | strength of the electric field when driving LD11e of the optical signal transmission part 11 was measured in each point of O-R of FIG. The measurement results are shown in Table 1.

In addition, O to R points in Table 1 are points on the stem 11b of the optical signal transmission unit 11 (near the input unit), points on the center of the housing 13, and on the end of the housing 13 on the optical transmission component 14 side. (A point in the vicinity of the YAG welded part), a point on the stem 12b of the optical signal receiving part 12 (in the vicinity of the output part).
As shown in Table 1, in the experiment, the electric field strength in the sample X2 decreases as it approaches the optical signal receiving unit 12 side of the circuit board 20, but the electric field strength measured at the point R is 78.5 dBμV / m. Further, the electric field intensity measured in the sample X3 is smaller at the O point and the P point than the sample X2, but is almost unchanged at the Q point and the R point.

  However, the electric field strength measured in Sample 1 is smaller at each of the points O to R than Samples X1 and X2, and is particularly 72.0 dBμV / m at the R point. Therefore, in the optical transceiver module 1, by providing the metal member 30 as described above, the electric field strength in the vicinity of a portion (such as a lead pin) that is susceptible to noise around the optical signal receiving unit can be reduced. I understand.

  As described above, in the optical transceiver module 1, since the electric field strength in the vicinity of the optical signal receiving unit is small, the electric potential in the vicinity of the optical signal receiving unit of the housing can be stably set to the GND potential to reduce electrical crosstalk. This is possible, and the influence of electromagnetic waves from the periphery of the optical signal transmitter (LD drive wiring portion), which is a main noise source, on the output portion of the optical signal receiver is small.

  Next, another example of the metal member will be described with reference to FIG. FIG. 3 is a perspective view of another example metal member. The metal member 40 of the present example is attached to the module main body 10 to reduce electrical crosstalk from the optical signal transmission unit 11 and the optical transmission / reception module is connected to the circuit board 20 similarly to the metal member 30 of the above example. It is also for mounting from one side. However, unlike the metal member 30, the metal member 40 includes two metal members (a first member 41 and a second member 44). The metal member 40 is used in a state where the second member 44 is assembled to the first member 41 as shown in FIG.

  The metal member 40 has an attachment portion 43 that is a portion for attaching (fixing) the metal member 40 to the circuit board 20, similar to the attachment portion 32 of the metal member 30. The attachment portion 43 is preferably fixed to the circuit board 20 by soldering similarly to the attachment portion 32 and is electrically connected to the SG of the circuit board 20. Further, unlike the attachment portion 32, an engagement hole 43 a with which the second member 44 is engaged is provided. By fitting the second member 44 into the first member 41 so that the engaging hole 43a and the engaging portion 46 of the second member 44 are engaged, the second member 44 is It is assembled to the member 41.

  The two members 41 and 44 have main body portions 42 and 45 having substantially semi-cylindrical shapes, respectively. When the first member 41 and the second member 44 are assembled, the main body portions 42 and 45 abut at least the housing 13 by sandwiching the module main body 10 from above and below. In other words, the metal member 40 is attached to the module body 10 such that the housing 13 of the module body 10 is sandwiched between the first member 41 and the second member 44. The metal member 40 is in contact with the housing 13 and is electrically connected to the housing 13.

When using the metal member 30 of the previous example, it was necessary to perform YAG welding in order to fix and electrically connect the main body portion 31 and the casing 13 of the module main body 10, but the metal member 40 is used as described above. By configuring as above, the YAG welding process can be omitted.
In addition, when using the metal member 30 of the previous example, since gold plating for soldering or the like becomes an obstacle when performing the YAG welding, partial plating is necessary. However, the metal member 40 is used as described above. By configuring, the whole may be subjected to a gold plating process or the like. In that case, for example, when the optical transceiver is manufactured, the partial plating cost becomes unnecessary, and thus the manufacturing cost can be reduced.

  In addition, the metal member 40 of this example is a material (for example) that can be easily bent as compared with the material of the metal member 30 so that the second member 44 can be easily assembled to the first member 41. For example, it is preferable to form phosphor bronze thinner than the metal member 30. The metal member 40 is attached to the module body 10 by sandwiching the housing 13 in such a form that the optical signal receiving part 12 of the module body 10 is sandwiched between both attachment parts 43.

  Further, the main body portion 42 of the first member 41 and the main body portion 45 of the second member 44 are cut to the optical signal receiving portion 12 side of the module main body 10 in the same manner as the main body portion 31 of the metal member 30 of the previous example. Notches 42a and 45a are respectively formed. These notches 42a and 45a form openings. This opening allows the metal member 40 to contact the optical signal receiving unit 12 when the metal member 40 is attached to the circuit board 20 regardless of the position of the optical signal receiving unit 12 in the module body 10 for alignment. You can avoid it.

  Moreover, in order to make the electrical connection between the metal member 40 and the module main body 10 more reliable, for example, a plurality of elastic pieces 42b are formed on the main body portion 42a. These elastic pieces 42b urge the module main body 10 in the direction toward the second member 44, and the metal pieces 40 and the module main body 10 can be physically and reliably brought into contact with each other by the elastic pieces 42b. ing. The elastic piece 42 is formed by being bent from the main body 42a.

  4 and 5 are diagrams for explaining an optical transceiver module according to another embodiment of the present invention. FIG. 4 (A) is a perspective view of the optical transceiver module, and FIG. 4 (B) is a plan view thereof. is there. FIG. 5A is a diagram showing the state in which the present optical transceiver module is attached to the circuit board with the metal member omitted, and FIG. 5B is an illustration of optical coupling in the optical transceiver module. It is a schematic diagram explaining a mode.

  As shown in FIG. 4, the optical transceiver module 2 includes a module main body 50 to which a metal member 60 used for fixing to a circuit board 80 (see FIG. 5) is attached. The module main body 50 of the present embodiment is, for example, a triplexer type optical transceiver module that transmits and receives an optical signal using a single optical fiber. In addition to transmitting and receiving a digital optical signal using a single optical fiber, Further, for example, another optical signal such as an analog modulation signal (CATV video signal or the like) can be received. The optical transmission / reception module 2 with the metal member 60 attached to the module body 50 can be attached to the circuit board 80 by fixing the metal member 60 to the circuit board 80.

  First, the module main body 50 and the circuit board 80 will be described with reference to FIG. As shown in FIG. 5A, the module main body 50 includes an optical signal transmission unit 51 that transmits an optical signal having a first wavelength, a first optical signal reception unit 52 that receives an optical signal having a second wavelength, It has a second optical signal receiver 53 that receives an optical signal of the third wavelength, a housing 54, an optical transmission component 55, and the like. Further, for example, the optical signal output from the module main body 50 is a digital modulation signal of the first wavelength, and the optical signal input to the module main body 50 includes the digital modulation signal of the second wavelength and the first wavelength. 3 is an analog modulation signal having a wavelength of 3.

  As shown in FIG. 5B, the optical signal transmitter 51 is equipped with an LD 11e that emits an optical signal having the first wavelength. The optical signal emitted from the LD 11e is transmitted through the condensing lens 11c and the condensing lens 11c. The light passes through a first WDM filter 54a and a second WDM filter 54b described later included in the housing 54, and is transmitted to the outside via the optical fiber 14a in the optical transmission component 14. Other shapes and configurations of the optical signal transmission unit 51 are the same as those of the optical signal transmission unit 11 in the embodiment of FIGS. 1 and 2.

  The first optical signal receiver 52 is equipped with a PD 12e that receives an optical signal of the second wavelength. The PD 12e receives an optical signal incident from an optical fiber 14a in the optical transmission component 14 and transmitted through the second WDM filter 54b and reflected by the first WDM filter 54a. Light is received through the filter 54c and the condensing lens 12c. Other shapes and configurations of the first optical signal receiving unit 52 are the same as those of the optical signal receiving unit 12 in the embodiment of FIGS. 1 and 2.

  The second optical signal receiving unit 53 is equipped with a PD 53a that receives an optical signal having the second wavelength. The PD 53a receives an optical signal incident from the optical fiber 14a in the optical transmission component 14 and reflected by the second WDM filter 54b, and a second cut filter 54d (to be described later) included in the housing 54 and a condensing lens 12c. And receive light via For example, an analog reception PIN photodiode can be used as the PD 53a. In the second optical signal receiving unit 53, the PD 53a is directly electrically connected to the lead pin 12a (that is, not via the TIA). Therefore, the signal received by the PD 53a and converted into an electrical signal is directly sent out of the optical signal receiving unit 53 via the lead pin 12a. Other shapes and configurations of the second optical signal receiving unit 53 are the same as those of the optical signal receiving unit 12 in the embodiment of FIGS. 1 and 2.

  The optical transmission component 55 emits signal light from the outside toward the optical signal transmitter 51 from its end face. Among these optical signals, the optical signal having the third wavelength is reflected by the second WDM filter 54 b and received by the PD 53 a of the second optical signal receiving unit 53. In addition, the optical signal having the second wavelength among the optical signals emitted from the optical transmission component is transmitted through the second WDM filter 54b, reflected by the first WDM filter 54a, and the first optical signal receiving unit 52. Is received by the PD 12e. Other shapes and configurations of the optical transmission component 55 are the same as those of the optical transmission component 14 in the embodiment of FIGS.

The casing 54 is provided with the optical signal transmitter 51, the first optical signal receiver 52, the second optical signal receiver 53, and the optical transmission component 55 as described above. Two WDM filters 54a and 54b and first and second cut filters 54c and 54d are also attached.
The first and second WDM filters 54a and 54b are wavelength selective filters that selectively transmit or reflect based on the wavelength of light.

The first WDM filter 54a transmits the optical signal having the first wavelength. Of the optical signal from one end of the optical fiber 14a, an optical signal having a second wavelength that has passed through a second WDM filter 54b described later is transmitted to the first optical signal receiving unit 52 by the first WDM filter 54a. Led.
The second WDM filter 54b reflects the optical signal having the third wavelength and transmits the optical signals having the first and second wavelengths. The second WDM filter 54 b guides the optical signal having the third wavelength among the optical signals input from one end of the optical fiber 14 a to the second optical signal receiving unit 53.

  The first and second cut filters 54c and 54d transmit light of a specific wavelength and block light of other wavelengths, transmit the second and third wavelengths, respectively, An optical signal having a wavelength other than the transmitting wavelength among the wavelengths 1 to 3 is blocked. The first and second cut filters 54c and 54d can prevent an optical signal having a wavelength other than a desired wavelength from entering the first and second optical signal receivers 52 and 53.

  The casing 54 to which the above components are attached is formed with an optical path hole 54e having a cylindrical axis as a central axis, and the first and second WDM filters 54a and 54b are fixed to the optical path hole 54e. . The housing 54 has first and second cut filter fixing holes 54f and 54g to which the first and second cut filters 54c and 54d are fixed.

  Further, the housing 54 has an optical signal transmitter fixing hole 54h and an optical transmission component fixing surface 54k similar to the optical signal transmitter fixing hole 13f and the optical transmission component fixing surface 13h of the embodiment of FIGS. . Moreover, it has the 1st optical signal receiving part fixing surface 54i and the 2nd optical signal receiving part fixing surface 54j similar to the optical signal receiving part fixing surface 13g of embodiment of FIG.1 and FIG.2.

  The optical signal transmitter 51 that emits the optical signal having the first wavelength is arranged along the first axis (the central axis of the casing 54) A by the casing 54. In addition, the first optical signal receiving unit 52 that receives the optical signal having the second wavelength is disposed along the second axis B that intersects the first axis A by the casing 54. The second optical signal receiving unit 53 that receives the optical signal having the third wavelength is arranged along a third axis C that is an axis that intersects the first axis A and is different from the second axis B. Is done.

  Further, the housing 54 allows the first optical filter (first WDM filter 54a) that transmits light of the first wavelength and reflects light of the second wavelength to pass through the first axis A and the second axis. It is arranged at a position intersecting with the axis B. The second optical filter (second WDM filter 54b) that reflects the optical signal of the third wavelength and transmits the optical signal of the first and second wavelengths has the first axis A and the third axis. Is arranged at a position intersecting with the axis C.

Further, the optical fiber 14a held by the optical fiber holding portion (ferrule 14b) along the first axis A is arranged at a position satisfying the following conditions (1) to (3) by the casing 54. The
(1) A position where light of the first wavelength emitted from the optical signal transmitter 51 is coupled to the optical fiber 14a after passing through the first and second optical filters.
(2) A position where the second wavelength light propagating through the optical fiber 14 a is reflected by the first optical filter and coupled to the first optical signal receiving unit 52.
(3) A position where the light of the third wavelength that has propagated through the optical fiber 14 a is reflected by the second optical filter and coupled to the second optical signal receiving unit 53.

That is, the housing 13 positions the optical signal transmitter 51, the first and second optical signal receivers 52 and 53, and the optical transmission component 55 so that the following (A) to (C) can be achieved. To be combined.
(A) The optical signal of the first wavelength emitted from the LD 11e of the optical signal transmission unit 51 enters the optical fiber 14a via the first and second WDM filters 54a and 54b and is transmitted to the outside.
(B) Of the optical signal emitted from the outside through the optical fiber 14 a, the optical signal having the third wavelength is reflected by the second WDM filter 54 b and is incident on the PD 12 e of the second optical signal receiving unit 53.
(C) Of the optical signal emitted from the outside through the optical fiber 14 a, the optical signal of the second wavelength is reflected by the second WDM filter 54 b and is incident on the PD 12 e of the second optical signal receiving unit 53.

The circuit board 80 is the same as the circuit board 20 of the embodiment of FIGS. 1 and 2, and is between the optical signal transmitter 51, the first optical signal receiver 52, and the second optical signal receiver 53. Then, send and receive electrical signals.
The optical transmission / reception module 2 having the module body 50 and attached to the circuit board 80 as described above has a metal member 60 (see FIG. 4) attached to the module body 50. For example, the metal member 60 is attached to the circuit board 80. It is possible to attach from one side of the circuit board 80 by soldering and connecting the lead pins 11a and 12a and the conductive pattern 22 of the circuit board 80 by soldering.

  Next, returning to FIG. 4, the metal member 60 according to the main part of the present invention will be described. The metal member 60 is attached to the module body 50 to reduce electrical crosstalk from the optical signal transmitter 51 of the optical transceiver module 2 and to attach the optical transceiver module 2 from one side of the circuit board 80. is there.

  The metal member 60 collectively covers a housing (housing portion) 55 that holds each of the optical signal transmitter 51, the optical signal receiver 52, and the optical transmission component 14 of the optical transceiver module 2. Are electrically connected to a signal ground (SG). The metal member 30 can be attached to the circuit board by an operation only from one side of the circuit board 20. As shown in FIG. 4A, the metal member 60 has a mounting portion 62 similar to the mounting portion 32 of the embodiment of FIGS. 1 and 2 and a main body portion 61.

  As shown in FIG. 4A, the main body 61 of the metal member 60 includes at least an optical signal transmission unit 51 of the module main body 50 and a housing continuing from the optical signal transmission unit 51 to the optical signal reception units 52 and 53. The body 54 is covered from one side of the module body 50. Also, the main body 61 differs from the main body 31 of the embodiment of FIGS. 1 and 2 as shown in FIG. 4B on both sides thereof (the first optical signal receiving unit 52 side and the second light). A notch 61a is formed on the signal receiving unit 53 side. Each of the notches 61a is similar to the notch 31a of the embodiment of FIGS. The other shapes and configurations of the main body 61 are the same as those of the main body 31 in the embodiment shown in FIGS.

  Then, the other example of the metal member of this embodiment is demonstrated using FIG. FIG. 6 is a perspective view of another example metal member. Similar to the metal member 60 of the above example, the metal member 70 of this example is attached to the module body 50 to reduce electrical crosstalk from the optical signal transmission unit 51, and the optical transmission / reception module is connected to the circuit board 80. It is for mounting on. However, unlike the metal member 60, it consists of two metal members (a first member 71 and a second member 74).

The first member 71 of the metal member 70 has a main body portion 72 and an attachment portion 73 similar to the main body portion 42 and the attachment portion 43 included in the first member 41 of the metal member 40 of the embodiment of FIG.
Further, the second member 74 of the metal member 70 is similar to the main body 45 and the engaging portion 46 of the second member 44 of the metal member 40 of the embodiment of FIG. Have

However, both the main body portions 72 and 75 have cutouts 72a and 75a on both sides (the first optical signal receiving unit 52 side and the second optical signal receiving unit 53), respectively. These notches 72 a and 75 a are configured to form openings on both sides of the metal member 70 when the second member 74 is assembled to the first member 71. With these openings, when the metal member 70 is attached to the circuit board 80, the first and second optical signal receivers 52 and 53 are arranged in the module body 50 for alignment. It is possible to prevent the second optical signal receivers 52 and 53 from touching.
Further, the metal member 70 is attached to the module main body 50 so that the housing 54 of the module main body 50 is sandwiched between the first member 71 and the second member 74. The metal member 70 is in contact with the housing 55 and is electrically connected to the housing 54.

  In the optical transceiver module according to the present embodiment, by providing such a metal member 70, the noise terminal voltage in the module body 50 can be reduced. This has been confirmed by the inventors' tests.

  In the test, an optical transceiver module having the configuration of the present embodiment (a metal member 70 is attached to the module body 50 so as to sandwich the casing 54, and the metal member 70 is electrically connected to the SG of the circuit board 80 to obtain a circuit. Sample Y1 was attached to the substrate 80). A sample Y2 having the same configuration as the sample Y1 except that the metal member 70 is not provided (the casing 54 and the SG are not electrically connected) was prepared. And about these samples Y1 and Y2, when driving LD11e of the optical signal transmission part 51, the noise terminal voltage was measured in each point of SW point of FIG.

  5 are points on the stem 11b of the optical signal transmission unit 51, points on the center of the casing 54, and points on the end of the casing 54 on the optical transmission component 55 side (YAG welding). A point on the stem 12b of the first optical signal receiving unit 52, and a point on the stem 12b of the second optical signal receiving unit 53.

  The noise terminal voltages measured at points S to W were approximately 74 dbμV, 75 dbμV, 71 dbμV, 73 dbμV, and 73 dbμV for the sample Y2, respectively, and approximately 68 dbμV, 65 dbμV, and 64 dbμV for the sample Y1, respectively. 66 dbμV and 64 dbμV. From this, it can be seen that in the optical transceiver module of this embodiment, by providing the metal member 70, the noise terminal voltage can be reduced and the electrical crosstalk can be reduced.

  Table 2 shows the minimum receiving sensitivity characteristics of the first optical signal receiving unit 52 included in the module main bodies 50 of the samples Y1 and Y2.

  As shown in Table 2, the first optical signal receiver 52 of the sample Y2 has an optical signal transmitter when the minimum reception sensitivity when the LD 11e of the optical signal transmitter 51 is not driven is −32.2 dBm. When the 51 LD 11e is driven, the minimum receiving sensitivity changes to -19.8 dBm, and the crosstalk penalty is as large as 12.4 dB.

On the other hand, the first optical signal receiving unit 52 of the sample Y1 sets the LD 11e of the optical signal transmitting unit 51 when the minimum receiving sensitivity when the LD 11e of the optical signal transmitting unit 51 is not driven is −30.8 dBm. When driven, the minimum receiving sensitivity changes to −28.3 dBm, and the crosstalk penalty is as very small as 2.5 dB.
From this, it can be seen that by providing the metal member 70 in the optical transceiver module of the present embodiment, electrical crosstalk can be reduced and the crosstalk penalty for the minimum reception sensitivity can be reduced.

  In addition, the LD 11e of the optical signal transmission unit 51 is not driven in order to confirm the influence of electrical crosstalk on the second optical signal reception unit (analog reception) 53 of the module main body 50 of the samples Y1 and Y2. And the CN ratio in a non-driven state. The comparison results are shown in Table 3.

As shown in Table 3, in Y2, by driving the LD 11e of the optical transmission / reception unit 51, the CN ratio decreases by 5 to 24.2 dB in a carrier frequency range of 55 to 800 MHz. That is, the electrical crosstalk from the optical transceiver 51 is 5 to 24.2 dB. On the other hand, in Y1, even if the LD 11e of the optical transmission / reception unit 51 is driven, the CN ratio hardly changes in the range of the carrier frequency of 55 to 800 MHz, and the electrical crosstalk from the optical transmission / reception unit 51 is −0. .3 to 2.0 dB.
From this, it can be seen that by providing the metal member 70 in the optical transceiver module of the present embodiment, electrical crosstalk can be reduced and the crosstalk penalty for the minimum reception sensitivity can be reduced.

  As described above, according to the present invention, the operation of attaching the single-fiber bidirectional optical module to the circuit board is facilitated. In addition, since the metal member covering the module covers not only the optical signal transmission unit but also the housing or the like, noise floating in a portion other than the optical signal transmission unit can be reduced, and the transmission unit of the optical transmission / reception module can It is possible to reduce electrical crosstalk of signals to the receiving unit. Therefore, it is possible to reduce the manufacturing cost of equipment such as an optical transceiver including a single fiber bidirectional optical module, and to obtain a good reception sensitivity characteristic and CN ratio.

In the above-described optical transceiver module, a method using soldering is used as a method for fixing the metal member to the circuit board. However, instead of this method, a method of fixing with a screw or the like may be used. Therefore, it is preferable that the metal member has a screw hole or a semicircular recess for screwing in the attachment portion.
Similarly, the connection method between the metal member and the optical transmission / reception module may be a method of fixing with screws instead of using YAG welding.
Further, the REET pin of the optical transceiver module and the conductive pattern of the circuit board may be electrically connected using a flexible printed circuit board.

It is a figure explaining the optical transmission / reception module which concerns on one Embodiment of this invention. It is a figure explaining the optical transmission / reception module which concerns on one Embodiment of this invention. It is a perspective view of the other example of the metal member of the optical transmission / reception module of embodiment of FIG.1 and FIG.2. It is a figure explaining the optical transmission / reception module which concerns on other embodiment of this invention. It is a figure explaining the optical transmission / reception module which concerns on other embodiment of this invention. It is a perspective view of the other example of the metal member of the optical transmission / reception module of embodiment of FIG.5 and FIG.6. It is a figure explaining the conventional optical transmission / reception module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 ... Single fiber bidirectional module (optical transmission / reception module), 10 ... Optical transmission / reception module main body (module main body), 11 ... Optical signal transmission part, 11a, 12a ... Lead pin, 11b, 12b ... Stem, 11c, 12c ... Condensing Lens 11d, 12d ... cap, 11e ... LD, 12e ... PD, 12 ... optical signal receiver, 13 ... housing, 13a ... WDM filter, 13b ... cut filter, 13c ... optical path hole, 13d ... WDM filter fixing part , 13e: Cut filter fixing hole, 13f: Optical signal transmission unit fixing hole, 13g: Optical signal receiving unit fixing surface, 13h: Optical transmission component fixing surface, 13i: Optical signal transmission unit fixing wall, 14 ... Optical transmission component, 14a ... Optical fiber, 14b ... Ferrule, 14c ... Sleeve, 20 ... Circuit board, 21 ... IC, 22 ... Conductive pattern, 30 ... Metal member, 31 Body part 31a ... Notch, 31b ... Opening, 32 ... Mounting part, 40 ... Metal member, 41 ... First member, 42, 45 ... Body part, 42a ... Notch 43 ... Mounting part, 43a ... Engagement hole , 44 ... second member, 46 ... engaging part, 50 ... optical transmission / reception module, 51 ... optical signal transmission part, 52 ... first optical signal reception part, 53 ... second optical signal reception part, 53a ... PD 54 ... casing, 54a ... first WDM filter, 54b ... second WDM filter, 54c ... first cut filter, 54d ... second cut filter, 54e ... optical path hole, 54f, 54g ... cut filter fixed Hole 54h: Optical signal transmitter fixing hole 54i Optical signal receiver fixing surface 54j Optical signal receiver fixing surface 54k Optical transmission component fixing surface 55 Optical transmission component 60 Metal member 61 Body part, 62 ... mounting part, 7 ... metal member, 71 ... first member, 72, 75 ... main body, 73 ... attaching portion, 74 ... second member, 76 ... engagement portion, 80 ... circuit board.

Claims (4)

A transmitter that transmits a first optical signal arranged along a first axis, and a receiver that receives a second optical signal arranged along a second axis that intersects the first axis And a first optical filter is disposed at an intersection of the first axis and the second axis, and the first optical signal is transmitted through an optical fiber disposed on the first axis. A single fiber bi-directional optical module for transmitting and receiving the second optical signal,
A single-fiber bidirectional optical module characterized in that a casing portion holding each of the transmitter, the receiver, and the optical fiber is covered with a common conductive metal member that can be attached from one side of a circuit board and grounded. .   A receiving unit configured to receive a third optical signal disposed along a third axis intersecting the first axis; and a second light at an intersection between the first axis and the third axis. The single-fiber bidirectional optical module according to claim 1, wherein a filter is disposed to receive the third optical signal via the optical fiber.   The single-fiber bidirectional optical module according to claim 1, wherein the conductive metal member has an opening for joining to the housing portion by welding.   3. The single core according to claim 1, wherein the conductive metal member includes two members each having a substantially cylindrical shape divided in half, and the casing portion is sandwiched and attached by the two members. Bidirectional optical module.

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