Optical transmission module, optical data link and optical transmission system

Abstract

To provide an optical transmission module, an optical data link, and an optical transmission system, the optical transmission module including a simplified matching circuit and a bias circuit having improved power efficiency.SOLUTION: There are provided: an optical transmission module (1) that includes a coupling unit (13) electromagnetically coupling a first line (11) having both ends to which a high-frequency signal input unit (14) and a termination unit (15) are connected with a second line (12) having both ends to which an electric-optic conversion unit (17) and a power supply connection unit (16) for a DC power supply are connected and makes a signal input from the high-frequency signal input unit entirely propagate into the electric-optic conversion unit on the second line from magnitude relation of attenuation amounts in coupling and isolation characteristics between the first line and the second line, or an optical transmission module including a matching resistor connected in parallel to an electric-optic conversion unit, a first capacitor for inhibiting DC current from flowing from a power supply connection unit for the DC power supply to the matching resistor, and a second capacitor connected in series between the high-frequency signal input unit and the matching resistor; an optical data link; and an optical transmission system.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical transmission module that transmits and receives an electrical signal via an optical transmission line, an optical data link using the same, and an optical transmission system using the optical data link. [Background technology]

[0002] In recent years, the demand for optical transmission systems capable of high-speed, large-capacity communication has been increasing with the rapid increase in Internet traffic. The optical transmission system is composed of data transmitting and receiving devices, an optical cable, and optical transmission modules connected to both ends of the optical cable, and an optical data link connecting the transmitting and receiving devices. The optical transmission module is composed of an optical signal transmitting module consisting of an electro-optical converter such as a semiconductor laser and a bias circuit for driving the converter in order to convert a received electrical signal into an optical signal, and an optical signal receiving module consisting of an opto-electrical converter such as a photodiode for receiving an optical signal and converting it into an electrical signal, a signal extraction circuit, etc.

[0003] 14 illustrates an equivalent circuit 100 of a conventional optical transmission module (transmission side) using a semiconductor laser. The equivalent circuit 100 includes at least a semiconductor laser 101, a bias circuit 102, and an impedance matching circuit 103 (see, for example, Patent Document 1 and Non-Patent Document 1). The bias circuit 102 is connected to a DC drive power source for applying a bias voltage to the semiconductor laser 101 to excite and oscillate it. The impedance matching circuit 103 matches the impedance of an AC signal input to the semiconductor laser 101.

[0004] In addition, in an optical transmission module that uses, for example, a vertical-cavity surface-emitting laser (VCSEL) as an electrical-optical conversion unit, a matching resistor is connected in parallel to the VCSEL in a bias circuit (for example, Patent Document 2, Non-Patent Document 2, and Non-Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-46179 [Patent Document 2] Japanese Patent Application Laid-Open No. 9-8583 [Non-Patent Document]

[0006] [Non-Patent Document 1] Yansheng Li, "Research on VCSEL Optical Output Stabilization Driving Circuit Method and LSI Implementation for Gb / s Optical Wiring," [online], March 2008, Kagoshima University, [searched on March 23, 2020], Internet, <http: / / ir.kagoshima-u.ac.jp / bitstream / 10232 / 4897 / 1 / %E6%9D%8E.pdf> [Non-Patent Document 2] V. Kozlov and A. C. Carusone, "Capacitively-Coupled CMOS VCSEL Driver Circuits," IEEE Jour. Solid-State Circuits, vol.51, no.9, pp.2077-2090, Sept.2016. [Non-Patent Document 3] MAX3735A Laser Driver Output Configurations, Part4: Driving VCSELs, Design Note :HFDN-26.3, Rev.1; 04 / 08(2004). Maxim Integrated [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] Incidentally, the characteristic impedance of a transmission line used in a high frequency system of several MHz or more is usually 50Ω (75Ω for a transmission line of a television or the like). And, because of the characteristic impedance of the transmission line, the conventional optical transmission module had to be provided with a matching circuit, as shown in the configuration of the equivalent circuit 100 in FIG. 14. Also, in order to supply a bias voltage, at least an inductor had to be inserted. Therefore, the number of parts increases, and depending on the frequency band used, it is difficult to select a coil, and the coil may become large, and further, the circuit becomes complicated, which may result in high costs. Also, there was an inconvenience that it goes against the recent demand for miniaturization.

[0008] The disclosure in this specification is intended to solve the above problems, and provides a low-cost, small-sized optical transmission module, an optical data link, and an optical transmission system by simplifying a circuit that constitutes an optical transmission module. The eyes The target. [Means for solving the problem]

[0009] In order to achieve the above object, a first aspect of the disclosure of this specification provides a first line having one end serving as a high-frequency signal input portion and the other end serving as a termination portion; a second line having an electro-optical conversion unit that converts an electrical signal input from the high frequency signal input unit into an optical signal and outputs the optical signal, and a power supply connection unit that is connected to a DC power supply and applies a voltage to drive the electro-optical conversion unit, each connected to one of both ends; a coupling section in which the first line and the second line are electromagnetically coupled to each other through a predetermined space with a predetermined electrical length for a wavelength of a frequency used; having Depending on the frequency band of the device you are connecting to, In a frequency band range in which the attenuation of the coupling characteristic between the first line and the second line is smaller than the attenuation of the isolation characteristic, the second line is connected to the electrical-optical converter at one end in a forward propagating direction of a traveling wave of a high frequency signal input from the high frequency signal input unit to the first line, and is connected to the power supply connector at the other end; In a frequency band range in which the attenuation of the coupling characteristic between the first line and the second line is greater than the attenuation of the isolation characteristic, The second line is connected to the electro-optical conversion unit at one end in a direction propagating in a reverse direction to the traveling wave of the high frequency signal input from the high frequency signal input unit to the first line, and is connected to the power supply connection unit at the other end. It is possible An optical transmission module is provided.

[0010] According to this configuration, by utilizing the fact that the relationship between the attenuation of the coupling characteristics and the isolation characteristics differs depending on the frequency band used, the high-frequency signal can be configured to propagate only to the electrical-to-optical conversion section, eliminating the need to provide an inductor in the electrical-to-optical conversion circuit in the optical transmission module.

[0011] The optical transmission module may have a photodiode connected to the high frequency signal input section as an optical-electrical conversion section, and may use a vertical cavity surface emitting laser (VCSEL) as the electrical-optical conversion section.

[0012] In addition, the first 2 In order to achieve the above object, the present invention provides a first line having a high-frequency signal input unit connected to one end and an optical-electrical conversion unit connected to the other end; a second line having an electro-optical conversion unit that converts an electrical signal input from the high frequency signal input unit into an optical signal and outputs the optical signal, and a power supply connection unit that is connected to a DC power supply and applies a voltage to drive the electro-optical conversion unit, each connected to one of both ends; a coupling section in which the first line and the second line are electromagnetically coupled to each other through a predetermined space with a predetermined electrical length for a wavelength of a frequency used; having Depending on the frequency band of the device you are connecting to, In a frequency band range in which the attenuation of the coupling characteristic between the first line and the second line is smaller than the attenuation of the isolation characteristic, the second line is connected to the electrical-optical converter at one end in a forward propagating direction of a traveling wave of a high frequency signal input from the high frequency signal input unit to the first line, and is connected to the power supply connector at the other end; In a frequency band range in which the attenuation of the coupling characteristic between the first line and the second line is greater than the attenuation of the isolation characteristic, The second line is an optical transmission module that connects the electrical-optical conversion unit to one end in a direction propagating in a reverse direction to the traveling wave of the high frequency signal input from the high frequency signal input unit to the first line, and connects the power supply connection unit to the other end; One or two optical cables connecting both ends of the optical transmission module; having The optical transmission modules connected to both ends each output an optical signal to the optical cable. The electrical-optical conversion unit and inputting an optical signal from the optical cable. The photoelectric conversion unit The present invention provides an optical data link capable of bidirectional optical transmission.

[0013] Further, the first aspect of the present disclosure 3 In order to achieve the above object, the third aspect provides an optical transmission system capable of transmitting an optical signal from a transmitting device to a receiving device via the optical data link. Effect of the Invention

[0014] According to the present invention, even without providing a matching circuit, due to the relationship between the attenuation amounts of the coupling characteristics and the isolation characteristics, depending on the frequency band used, the high-frequency signal propagates only to the electrical-optical conversion section, thereby achieving the effect of providing a low-cost, small-sized optical transmission module, optical data link, and optical transmission system. [Brief description of the drawings]

[0015] [Figure 1]FIG. 1 is a diagram showing a schematic circuit configuration of an optical transmission module according to the present embodiment, in which (A) shows the propagation direction of a high-frequency signal when the electrical length of a coupling part is λ / 4, and (B) shows the propagation direction of a high-frequency signal when the electrical length of a coupling part is shorter than λ / 4. [Diagram 2] FIG. 2 is a diagram illustrating a modified example of the circuit configuration of the optical transmission module according to the present embodiment. [Diagram 3] 3A and 3B are diagrams showing schematic diagrams of a specific example for explaining the function of the optical transmission module according to the present embodiment, in which (A) is a configuration diagram of a specific example of the optical transmission module of FIG. 1A, and (B) is a configuration diagram of a specific example of the optical transmission module of FIG. 1B. [Figure 4] FIG. 4 is a graph showing the propagation characteristics of each port of the optical transmission module in the specific embodiment of FIG. 3, using S parameters. [Diagram 5] FIG. 5 is a partial enlarged view showing a schematic diagram of a coupling portion of this embodiment, in which (A) is a partial enlarged view of a coupling portion arranged in parallel with a total electrical length of λ / 4, and (B) is a partial enlarged view of a coupling portion in which the parallel arrangement of (A) is shifted in the horizontal direction. [Figure 6] FIG. 6 is a graph showing the propagation characteristics of each port using S parameters for the coupling portion of FIG. 5(A), where (A) is a graph showing the propagation characteristics when the distance of space D is 1.2 mm, (B) is a graph showing the propagation characteristics when the distance of space D is 0.7 mm, and (C) is a graph showing the propagation characteristics when the distance of space D is 0.17 mm. [Figure 7] FIG. 7 is a graph showing the propagation characteristics of each port using S parameters for the coupling portion of FIG. 5(B), where (A) is a graph showing the propagation characteristics when the distance of space D is 1.2 mm, (B) is a graph showing the propagation characteristics when the distance of space D is 0.7 mm, and (C) is a graph showing the propagation characteristics when the distance of space D is 0.17 mm. [Figure 8] FIG. 8 is a schematic diagram of a specific example of the optical transmission module of this embodiment formed with a three-layer substrate, where (A) is a side cross-sectional view and (B) is a top view showing a schematic view of the coupling portion of the upper dielectric substrate. [Figure 9]FIG. 9 is a graph showing the characteristics of the optical transmission module of FIG. 8, where (A) is a graph showing the frequency characteristics of port P3, (B) is a graph showing the frequency characteristics of port P4, and (C) is a graph showing the directivity. [Figure 10] FIG. 10 shows an optical data link, where (A) is an external view of the optical data link, and (B) is a schematic diagram of the optical data link. [Figure 11] Figure 11 is a block diagram of an optical transmission system that connects a 4K camera, a camera media server, and a local 5G base station system via an optical data link. [Figure 12] FIG. 12 is an equivalent circuit diagram of an electrical-optical conversion circuit of the optical transmission module according to the second embodiment. [Figure 13] FIG. 13 is an equivalent circuit diagram of a modified example of the electrical-optical conversion circuit of the second embodiment. [Figure 14] FIG. 14 is a diagram showing an equivalent circuit on the transmission side of a conventional optical transmission module. [Figure 15] FIG. 15 is a diagram showing an equivalent circuit of a bias circuit of a conventional optical transmission module, where (A) is an equivalent circuit diagram when there is one matching resistor, and (B) is an equivalent circuit diagram when there are two matching resistors. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the embodiments for carrying out the disclosure of this specification will be described with reference to the drawings. When a subsequent embodiment has a component corresponding to an embodiment described earlier, the same reference numerals are used and duplicated description is omitted. In addition, when only a part of the configuration is described in each embodiment, the reference numerals of the previously described embodiment may be used for other parts of the configuration. Even if it is not clearly stated that each embodiment can be specifically combined, it is also possible to partially combine the embodiments as long as there is no particular problem with the combination. In addition, the size of each member in the drawings is appropriately emphasized to facilitate the description, and does not indicate the actual dimensions or ratio between the members. Further areas of applicability will become apparent from the description provided herein.The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

[0017] <Embodiments of the optical transmission module disclosed in this specification> Fig. 1 is a diagram showing a schematic diagram of a circuit configuration of an optical transmission module 1 and an optical transmission module 2 according to the present embodiment. The optical transmission module 1 in Fig. 1(A) has a first line 11, a second line 12, and a coupling section 13 arranged in parallel with the first line 11 and the second line 12 via a predetermined space capable of electromagnetically coupling the first line 11 and the second line 12 so that the electrical length L is λ / 4.

[0018] The first line 11 has one end serving as the high-frequency signal input unit 14 and the other end serving as the termination unit 15. The termination resistance of the termination unit 15 is, for example, the characteristic impedance of the first line 11. On the other hand, the second line 12 has one end serving as the power supply connection unit 16 and the other end serving as the electrical-optical conversion unit 17. The electrical-optical conversion unit 17 converts the electrical signal input from the high-frequency signal input unit 14 into an optical signal and outputs it. The power supply connection unit 16 is connected to a DC power supply and applies a voltage to drive the electrical-optical conversion unit 17. In addition, in order to prevent the voltage of the power supply connection unit 16 from fluctuating when the circuit is operating, a bypass capacitor 18 may be provided to connect the second line 12 to the ground. Specifically, for example, a feedthrough capacitor may be attached between the second line 12 and the metal case of the optical transmission module 1.

[0019] The dashed arrow (arrow pointing from high frequency signal input unit 14 to termination unit 15) on first line 11 indicates the direction of propagation of the high frequency signal (traveling wave). On the other hand, the dashed arrow (arrow pointing from power supply connection unit 16 to electrical-optical conversion unit 17) on second line 12 indicates the direction of propagation of the high frequency signal transmitted via coupling unit 13 when electrical-optical conversion unit 17 is driven by a voltage applied from a DC power supply (not shown) connected to power supply connection unit 16. In FIG. 1(A), the direction of the dashed arrow on second line 12 is the same as the forward direction of the arrow on first line 11.

[0020] The optical transmission module 2 in FIG. 1(B) has a first line 21, a second line 22, and a coupling portion 23 arranged in parallel on the surface of a circuit board S2, with a predetermined space between the first line 21 and the second line 22 allowing electromagnetic coupling therebetween, so that the electrical length L is shorter than λ / 4.

[0021] 1(A), one end of the first line 21 is a high-frequency signal input section 24, and the other end is a termination section 25. Similarly to Fig. 1(A), one end of the second line 22 is a power supply connection section 26, and the other end is an electrical-optical conversion section 27. Furthermore, for the same purpose as Fig. 1(A), a bypass capacitor 28 is provided to connect the second line 22 to ground.

[0022] The dashed arrow on the first line 21 (the arrow pointing in the direction from the high frequency signal input unit 24 to the termination unit 25) indicates the direction in which the high frequency signal propagates (traveling wave). On the other hand, the dashed arrow on the second line 22 (the arrow pointing in the direction from the power supply connection unit 26 to the electro-optical conversion unit 27) indicates the direction in which the high frequency signal propagates when the electro-optical conversion unit 27 is driven by the voltage applied from the power supply connection unit 26 and transmitted via the coupling unit 23. In FIG. 1(B), the direction of the dashed arrow on the second line 22 is opposite to that of the arrow on the first line 21.

[0023] The first line 11, the first line 21, the second line 12, and the second line 22 may be any transmission line that transmits electromagnetic waves, and may be formed of, for example, a microstrip line or a coplanar line.

[0024] 1(A) and 1(B) show a form in which the first line and the second line are formed on the same plane, but the first line, the second line and the coupling section may be formed on a multilayer board, for example, a three-layer board consisting of a first dielectric board, a second dielectric board and a third dielectric board. That is, the first line 11 (or the first line 21) is formed on one surface of the first dielectric board, and the high-frequency signal input section 14 (or the high-frequency signal input section 24) and the termination section 15 (or the termination section 25) are disposed on the other surface. The second line 12 (or the second line 22) is formed on one surface of the second dielectric board, and the power supply connection section 16 (or the power supply connection section 26) and the electro-optical conversion section 17 (or the electro-optical conversion section 27) are disposed on the other surface. A three-layer board may be formed by stacking the first and second dielectric boards so that one surface of the first dielectric board faces one surface of the second dielectric board with the third dielectric board interposed therebetween. At this time, the thickness of the third dielectric substrate becomes the coupling portion 13 (or coupling portion 23).

[0025] As described above, in the optical transmission module 1 and the optical transmission module 2 disclosed in this specification, the first line 11 (or the first line 21) and the second line 12 (or the second line 22) have a directional coupler-type structure, and high-frequency signals can be propagated in the desired direction on the second line 12 or the second line 22 in accordance with the high-frequency characteristics, and high-frequency signals are prevented from flowing into the power supply connection part 16, the power supply connection part 26, so there is no need to provide a matching circuit including an inductor or the like.

[0026] < Disclosed herein Optical Transmission Module Fruit Modifications of the embodiment> FIG. 2 is a diagram illustrating a schematic diagram of an optical transmission module 3 which is a modified example of the present embodiment.

[0027] The optical transmission module 3 has a three-layer substrate structure consisting of a lower layer substrate S31, an upper layer substrate S32, and an intermediate layer substrate S33. The lower layer substrate S31 has a first line 31 having a high-frequency signal input unit 34 at one end. The upper layer substrate S32 has a second line 32 having a power supply connection unit 36 ​​at one end and an electrical-optical conversion unit 37 at the other end. The intermediate layer substrate S33 has a microstrip antenna 35 formed thereon and is disposed at the end of the first line 31. Note that a bypass capacitor 38 may be connected to the end of the second line 32 to which the power supply connection unit 36 ​​is connected in order to prevent the voltage of the power supply connection unit 36 ​​from fluctuating when the circuit is operating.

[0028] The microstrip antenna 35 is resonantly coupled to the second line 32 with a predetermined electrical length (λ / 4 in this embodiment) to form a coupling section 33. In this embodiment, a high-frequency signal input from a high-frequency signal input section 34 to the first line 31 passes through the microstrip antenna 35 and propagates in the second line 32 in the same direction as the forward direction of the high-frequency signal of the first line 31, and the component is converted into an optical signal by an electrical-optical converter 37.

[0029] <Frequency characteristics of the optical transmission module according to this embodiment> Hereinafter, the frequency characteristics of the optical transmission module according to this embodiment will be described with reference to Fig. 3 to Fig. 9. Fig. 3(A) shows an optical transmission module 1A according to a specific example of the optical transmission module 1 described in Fig. 1(A), and Fig. 3(B) shows an optical transmission module 2A according to a specific example of the optical transmission module 2 described in Fig. 1(B).

[0030] 3A, the optical transmission module 1A has four ports, port P1 to port P4. Port P1 and port P2 are adjacent to each other and are physically connected to each other at both ends of a first line 11A formed in a U-shape. Similarly, port P3 and port P4 are adjacent to each other and are physically connected to each other at both ends of a second line 12A formed in a U-shape. The closed ends of the first line 11A and the second line 12A formed in the U-shape are arranged in parallel to face each other with a predetermined space D between them, and form a coupling part 13A that is electromagnetically coupled.

[0031] A port P1 connected to one end of the first line 11A is a transceiver 14A such as an antenna that functions as a high-frequency signal input unit. A port P2 connected to the other end of the first line 11A is a terminal of the transceiver 14A, and has an optical-electrical converter 15A in this embodiment. The optical-electrical converter 15A is, for example, a photodiode, and receives an optical intensity modulated signal from an optical cable (not shown). As shown by a black arrow W1, the optical intensity modulated signal is input to the port P2 from the optical cable, converted into an electrical signal by the optical-electrical converter 15A, propagates through the first line 11A to the port P1, and the electrical signal is transmitted to a connected device (not shown) via the transceiver 14A connected to the port P1.

[0032] The port P3 connected to one end of the second line 12A has an electrical-optical converter 17A. The electrical-optical converter 17A is, for example, a vertical cavity surface emitting laser (VCSEL), and is connected to an optical cable (not shown) to output an optical intensity modulated signal. The port P4 connected to the other end of the second line 12A is a power supply connector 16A. As shown by the outlined arrow W2, a high-frequency signal (electrical signal) received by the transceiver 14A connected to the port P1 propagates in the direction of the port P2 on the first line 11A, and propagates in the direction of the port P3 of the second line 12A via the coupling section 13A (i.e., in the forward direction of the propagation direction of the first line 11A). Furthermore, a predetermined voltage is applied from a DC power supply (not shown) connected to the power supply connector 16A of the port P4 to excite and oscillate the electrical-optical converter 17A, and a DC component is added to the high-frequency signal and supplied to the electrical-optical converter 17A. The high frequency signal is converted into an optical intensity modulated signal by the electrical-to-optical converter 17A and output to the optical cable.

[0033] Referring to FIG. 3(B), like the optical transmission module 1A, the optical transmission module 2A has four ports, port P1 to port P4, and the U-shaped first line 21A and second line 22A are arranged in parallel facing each other at the closed end side of the U-shape with a predetermined space D between them, forming an electromagnetically coupled coupling portion 23A.

[0034] Similarly to the optical transmission module 1A, the port P1 connected to one end of the first line 21A is the transceiver 24A, and the port P2 connected to the other end of the first line 21A is the terminal of the transceiver 24A, and has an opto-electrical converter 25A in this embodiment. The opto-electrical converter 25A, such as a photodiode, is connected to an optical cable (not shown) and receives an optical intensity modulated signal. As shown by the black arrow W3, the optical intensity modulated signal is input to the port P2 from the optical cable, converted to an electrical signal by the opto-electrical converter 25A, propagates through the first line 21A to the port P1, and the electrical signal is transmitted to a connected device (not shown) via the transceiver 24A connected to the port P1.

[0035] The port P3 connected to one end of the second line 22A is the power supply connection section 26A. The other end of the second line 22A is an electrical-optical conversion section 27A such as a VCSEL, which is connected to an optical cable (not shown) and outputs an optical intensity modulated signal. As shown by the outlined arrow W4, a high-frequency signal (electrical signal) received by the transceiver section 24A connected to the port P1 propagates in the direction of the port P2 on the first line 21A and propagates in the direction of the port P4 of the second line 22A via the coupling section 23A (i.e., in the opposite direction to the propagation direction of the first line 21A). Furthermore, a predetermined voltage is applied from a DC power supply (not shown) connected to the power supply connection section 26A of the port P3 to excite and oscillate the electrical-optical conversion section 27A, and a DC component is added to the electrical signal and supplied to the electrical-optical conversion section 27A. The electrical signal is converted to an optical intensity modulated signal by the electrical-optical conversion section 27A and output to the optical cable.

[0036] FIG. 4 is a graph showing the propagation characteristics of each port of the optical transmission module 1A and the optical transmission module 2A in the specific example of FIG. 3, using S parameters.

[0037] The graph in Fig. 4 has frequency (GHz) on the horizontal axis and attenuation (dB) on the vertical axis, and shows characteristic values ​​for the four ports P1 to P4 of the optical transmission module 1A and the optical transmission module 2A in Fig. 3, with the output (insertion loss) of the signal propagating from P1 to P2 being S21, the output (coupling characteristic) of the signal propagating from P1 to P3 being S31, and the output (isolation characteristic) of the signal propagating from P1 to P4 being S41. Note that the electrical length of the coupling unit 13A and the coupling unit 23A is λ / 4 with respect to the wavelength of the transmission path at the specified frequency.

[0038] According to the graph of FIG. 4, in the frequency band range where the attenuation of the isolation characteristic S41 is smaller than the attenuation of the coupling characteristic S31, the propagation direction of the high frequency signal is opposite between the first line and the second line. Therefore, in the frequency band range, as in the optical transmission module 2A of FIG. 3(B), the electro-optical conversion unit 27A may be connected to the port P4, and the port 3 side may be the power supply connection unit 26A. On the other hand, in the frequency band range where the attenuation of the isolation characteristic S41 is larger than the attenuation of the coupling characteristic S31, the propagation direction of the high frequency signal is forward between the electro-optical conversion unit first line and the second line. Therefore, in the frequency band range, as in the optical transmission module 1A of FIG. 3(A), the electro-optical conversion unit 17A may be connected to the port P3, and the port 4 side may be the power supply connection unit 16A. In other words, if the frequency at which the isolation characteristic S41 and the coupling characteristic S31 intersect is defined as the boundary frequency f0, when the frequency of the input high-frequency signal is smaller than f0, the optical transmission module 2A is used, and when the frequency of the input high-frequency signal is larger than f0, the optical transmission module 1A is used.

[0039] 5 is a partial enlarged schematic diagram of the coupling part 13A of the optical transmission module 1A and the coupling part 23A of the optical transmission module 2A according to the specific embodiment of FIG. 4, (A) is a partial enlarged view of the coupling parts arranged in parallel with a total electrical length λ / 4 as the wavelength λ at the specified frequency, and (B) is a partial enlarged view of the coupling part in which the parallel arrangement of (A) is shifted in the horizontal direction. Also, FIG. 6 is a graph showing the propagation characteristics of each port (port P2, port P3, port P4) when the distance of the space D of the coupling part in FIG. 5(A) is changed using S parameters. Furthermore, FIG. 7 is a graph showing the propagation characteristics of each port (port P2, port P3, port P4) when the distance of the space D of the coupling part in FIG. 5(B) is changed using S parameters. In addition, in Figures 6(A) and 7(A), D = 1.2 mm, in Figures 6(B) and 7(B), D = 0.7 mm, and in Figures 6(C) and 7(C), D = 0.17 mm.

[0040] According to the graph in Figure 6, the boundary frequency f0 is approximately 2.5 GHz in (A), approximately 3 GHz in (B), and three boundary frequencies occur between 3 and 7 GHz in (C). As for the change in attenuation, the effect of the difference in spatial distance D is small in the forward direction S31 (coupling characteristics), but in the reverse direction S41 (isolation characteristics), there is a tendency for the attenuation to decrease as the spatial distance D becomes narrower.

[0041] From the above, when the operating frequency is smaller than the boundary frequency f0, the output of S41 increases as the space D between the coupling portions 13A and 23A becomes narrower.

[0042] Next, according to the graph in Fig. 7, the boundary frequency f0 is approximately 4.5 GHz in (A), approximately 5.5 GHz in (B), and approximately 7.5 GHz in (C). As with Fig. 6, the change in attenuation is small in the forward direction S31 (coupling characteristics) due to the difference in spatial distance D, but in the reverse direction S41 (isolation characteristics), the attenuation tends to decrease as the spatial distance D becomes narrower.

[0043] When the operating frequency is less than the boundary frequency f0, the narrower the space D between the coupling parts 13A and 23A, the more the boundary frequency f0 shifts to the higher frequency side, and the smaller the attenuation of S41 becomes, so the larger the output becomes. Furthermore, the difference between S31 and S41 also becomes larger. From the above, the optimal space D between the coupling parts 13A and 23A can be determined.

[0044] Fig. 8 is a schematic diagram of a specific example in which the optical transmission module of this embodiment is formed with a three-layer dielectric substrate, (A) is a side cross-sectional view, and (B) is a top view showing a schematic view of the coupling part of the upper-layer dielectric substrate. Fig. 9 is a graph showing each characteristic of the optical transmission module of Fig. 8, (A) is a graph showing the frequency characteristic of port P3, (B) is a graph showing the frequency characteristic of port P4, and (C) is a graph showing the directivity.

[0045] The optical transmission module 3A in Fig. 8 has the same basic configuration as the optical transmission module 2A in Fig. 3(B), so detailed description of the overlapping configuration will be omitted. The upper layer dielectric substrate S31A of the optical transmission module 3A has a surface formed of a metal plate, and is formed with a port P1 and a port P2. The port P1 is a transmitting / receiving unit 34A, and the port P2 is connected to an optical / electrical conversion unit 35A.

[0046] The lower dielectric substrate S32A also has a surface formed of a metal plate, and is provided with ports P3 and P4. The port P4 is connected to an electrical-to-optical conversion unit 37A, and the port P3 is a power supply connection unit 36A to which a DC power supply can be connected.

[0047] The first line 31A is formed on the upper surface of the intermediate dielectric substrate S33A, i.e., on the opposing surface of the back surface of the upper-layer dielectric substrate S31A, and the second line 32A is formed on the upper surface of the lower-layer dielectric substrate S32A, i.e., on the opposing surface of the intermediate dielectric substrate S33A.

[0048] The upper dielectric substrate A31A and the lower dielectric substrate S32A have a thickness T1. The intermediate dielectric substrate S33A has a thickness T2 which corresponds to the space D in FIG. 3 and forms a coupling portion 33A together with the first line 31A and the second line 32A.

[0049] FIG. 8(B) shows the line length L and line width W of the first line 31A formed on the intermediate dielectric substrate S33A. Although FIG. 8(B) shows the line length L and line width W of the first line 31A, the second line 32A also has the same line length L and line width W (not shown. Also, they may be different from the width W of the first line 31A). Also, in FIG. 8(A), as in FIG. 3(B), an optical intensity modulated signal input to the photoelectric conversion unit 35A propagates from port P2 to port P1 as shown by a solid black arrow W5. On the other hand, as shown by a hollow arrow W6, a high-frequency signal received by the transceiver unit 34A connected to port P1 propagates in the first line 31A toward port P2, and propagates through the coupling unit 33A toward port P4 of the second line 32A (i.e., the opposite direction to the propagation direction of the first line 31A). As in the embodiment of FIG. 3(A), there is also a configuration (not shown) in which an electric signal propagates in the second line in the same direction as the electric signal propagates in the first line.

[0050] Fig. 9 is a graph showing each characteristic of the optical transmission module of Fig. 8. Fig. 9(A) is a graph showing the frequency characteristic of port P3 of the optical transmission module 3A of Fig. 8, where the horizontal axis is frequency (GHz) and the vertical axis is attenuation (dB) showing the coupling characteristic S31 from port P1 to port P3. The thickness T1 of the upper layer dielectric substrate A31A and the lower layer dielectric substrate S32A is 0.8 mm, and the thickness T2 of the intermediate dielectric substrate S33A is 1.2 mm. The difference in the coupling characteristic is compared when the line width W is 0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm.

[0051] Fig. 9(B) is a graph showing the frequency characteristics of port P4 of the optical transmission module 3A of Fig. 8, where the horizontal axis is frequency (GHz) and the vertical axis is attenuation (dB) showing the isolation characteristics S41 from port P1 to port P4. The thickness T1 of the upper layer dielectric substrate A31A and the lower layer dielectric substrate S32A and the thickness T2 of the intermediate dielectric substrate S33A are the same as in Fig. 9(A). The setting of the line width W is also the same as in Fig. 9(A), and the difference in the isolation characteristics is compared.

[0052] Fig. 9(C) is a graph showing the directional characteristics of the optical transmission module 3A in Fig. 8, where the horizontal axis is frequency (GHz) and the vertical axis is the amount (dB) showing the directional characteristics of the ports P3 and P4. The line width W is 1.0 mm, and the thickness T1 of the upper layer dielectric substrate A31A and the lower layer dielectric substrate S32A is 0.8 mm. The difference in the directional characteristics is compared when the thickness T2 of the intermediate dielectric substrate S33A is 0.8 mm, 1.2 mm, 1.6 mm, 2.4 mm, and 3.2 mm.

[0053] From the graph of FIG. 9, it can be seen that when the thickness T2 of the intermediate dielectric substrate S33A (ie, the coupling portion 33A) is set to 1.2 mm, there is a large difference between the coupling characteristic S31 and the isolation characteristic S41.

[0054] As described above, the optical transmission module according to the present embodiment disclosed in this specification can achieve low cost and miniaturization because, without the need for a matching circuit, high-frequency signals are propagated only to the electrical-to-optical conversion section depending on the frequency band used due to the relationship between the attenuation amounts of the coupling characteristics and the isolation characteristics.

[0055] <Optical data link> FIG. 10 shows an optical data link, where (A) is an external view of the optical data link, and (B) is a schematic diagram of the optical data link.

[0056] The optical data link 4 is composed of optical transmission modules 41 and 42 having any of the circuit configurations described with reference to FIGS. 1 to 9, and an optical cable 43 connecting the optical transmission modules 41 and 42.

[0057] Both the optical transmission module 41 and the optical transmission module 42 have a transceiver unit such as an antenna (corresponding to a high-frequency signal input / output unit) and an optical-electrical conversion unit, for example, a photodiode (corresponding to a termination unit), connected to both ends of a first line, a power supply connection unit and an electrical-optical conversion unit, for example, a vertical cavity surface emitting laser, connected to both ends of a second line, and a coupling unit that electromagnetically couples between the first line and the second line.

[0058] That is, the optical transmission module 41 and the optical transmission module 42 are configured to integrally include both devices, a vertical cavity surface emitting laser and a photodiode. Therefore, the optical data link 4 disclosed in this specification has optical transmission modules 41 and 42 at both ends each equipped with an E / O conversion processing unit that outputs an optical signal to the optical cable 43 and an O / E conversion processing unit that inputs an optical signal from the optical cable 43, and enables bidirectional optical transmission by selecting the connection destination.

[0059] In the optical transmission module 41 and the optical transmission module 42, in a frequency band range in which the attenuation of the coupling characteristic between the first line and the second line is smaller than the attenuation of the isolation characteristic, the second line has the electro-optical conversion unit at one end in a forward propagating direction with respect to the traveling wave of the high frequency signal input from the high frequency signal input unit to the first line, and has the power supply connection unit at the other end. On the other hand, in a frequency band range in which the attenuation of the coupling characteristic between the first line and the second line is larger than the attenuation of the isolation characteristic, the second line has the electro-optical conversion unit at one end in a reverse propagating direction with respect to the traveling wave of the high frequency signal input from the high frequency signal input unit to the first line, and has the power supply connection unit at the other end. Therefore, one having any of the above configurations may be selected according to the frequency band of the device to be connected using the optical data link 4.

[0060] 10B, the optical transmission modules 41 and 42 are connected to both ends of one or two optical cables 43 via optical connectors 44. The optical transmission module 41 functions as an E / O conversion processor, and when a high-frequency signal is input from the outside, the signal is converted into an optical signal by a vertical cavity surface emitting laser 412 from a transmitting circuit 411 and transmitted to the optical cable 43. On the other hand, the optical transmission module 42 functions as an O / E conversion processor, and when the optical signal is received from the optical cable 43, the optical signal is converted into an electrical signal by a photodiode 422, and the high-frequency signal is output to a connection destination by a receiving circuit 421.

[0061] <Optical transmission system> Figure 11 is a block diagram showing an example of an optical transmission system in which a 4K camera, a camera media server, and a local 5G base station system are connected via an optical data link.

[0062] The optical transmission system 5 is composed of a 4K camera C as a transmitting device that outputs a high-frequency signal, an optical data link 4 composed of an optical transmission module 41 that converts the high-frequency signal into an optical signal, an optical cable 43 that transmits the optical signal to the optical transmission module 42, and an optical transmission module 42 that converts the optical signal received from the optical cable 43 into an electrical signal, and a camera media server S as a receiving device that inputs the converted electrical signal.

[0063] Furthermore, the optical transmission system 5 disclosed in this specification receives an electrical signal at the camera media server S from the Wi-Fi (registered trademark) antenna of the camera media server S at antenna A via router R, converts this electrical signal back into an optical signal via the optical data link 4, converts it back into an electrical signal, transmits it to the base station system B, and distributes it over a wide area Internet line.

[0064] The frequency band used between the 4K camera C and the camera media server S is different from the frequency band used between the antenna A and the base station system B. The optical data link 4 can accommodate a variety of frequency bands by selecting the optical transmission modules 41 and 42 according to the frequency used, making it possible to configure the optical transmission system 5.

[0065] <Other> 15(A) and (B) show circuits 200 and 300 of an optical transmission module having a conventional bias circuit using a VCSEL. The portions surrounded by dashed lines are bias T circuits 214 and 314, respectively. The high-frequency signal input from input terminal 210 or input terminal 310 has low-frequency components removed by capacitor 214B or capacitor 314B. On the other hand, when a DC voltage V DC When the bias voltage Vcc is applied to the bias T circuit 214 or the bias T circuit 314, the high frequency components of the DC component flowing through the bias T circuit 214 or the bias T circuit 314 are removed by the inductor 214A or the inductor 314A. In addition, in FIG. 15(B), an RLC series circuit is formed and a matching resistor 314C is connected. The DC component is then added to the high frequency signal and supplied to the VCSEL 211 or the VCSEL 311. At this time, the matching resistor 212 or the matching resistors 312 and 314C are inserted to match the characteristic impedance with the VCSEL 311.

[0066] However, the equivalent resistance of the VCSEL at high frequencies is usually about 100Ω or more, while the matching resistor is about 100Ω or less. Therefore, the DC current flowing through the matching resistor is larger than the DC current flowing through the VCSEL, and the power consumption of the DC power supply is mostly consumed by the matching resistor. As a result, the power efficiency of the entire circuit is very poor. Furthermore, if the corresponding power value of the matching resistor is increased to meet the required power consumption of the matching resistor, the matching resistor becomes physically large, making it difficult to configure the matching resistor in a pattern. For this reason, the matching resistor is attached to the wiring path as a chip resistor, but there is an inconvenience that the high-frequency characteristics of the optical transmission module equipped with the chip resistor are deteriorated.

[0067] Hereinafter, as shown in FIG. 12 and FIG. 13, an optical transmission module that improves the power efficiency of a bias circuit and enhances high-frequency characteristics will be described.

[0068] 12 is an equivalent circuit diagram of the electrical-optical conversion circuit of the optical transmission module. The electrical-optical conversion circuit 6 is composed of a high-frequency signal circuit and a bias circuit.

[0069] The high frequency signal circuit has a high frequency signal input section 62A, and an electrical-to-optical conversion section 62C (for example, a vertical cavity surface emitting laser) that converts the electrical signal input from the high frequency signal input section 62A into an optical signal and outputs it.

[0070] On the other hand, the bias circuit is composed of a power supply connection unit 61A that applies a bias voltage to the electrical-optical conversion unit 62C to excite it, and a bias T circuit 61. The bias T circuit 61 is connected in series between a DC power supply connected to the power supply connection unit 61A and the electrical-optical conversion unit 62C, and has an inductor 61B that blocks the flow of a high-frequency signal from the high-frequency signal input unit 62A to the power supply connection unit 61A, and a first capacitor 61C that prevents a large DC current from flowing into the high-frequency signal input unit 62A. In other words, the bias T circuit 61 is formed to eliminate mutual influence between the high-frequency signal circuit and the bias circuit.

[0071] A matching resistor 62B is connected in parallel to the electro-optical conversion unit 62C between the high frequency signal input unit 62A and the electro-optical conversion unit 62C in order to match the characteristic impedance of the high frequency signal circuit with the electro-optical conversion unit 62C.

[0072] Furthermore, since the matching resistor 62B is connected in series with the inductor 61B and the first capacitor 61C, a direct current is prevented from flowing from the power supply connection portion 61A.

[0073] Furthermore, the matching resistor 62B is connected in series with a second capacitor 62D between the matching resistor 62B and the high frequency signal input section 62A. The second capacitor 62D prevents a direct current from flowing through the matching resistor 62B even if the direct current is present in the high frequency signal input section 62A.

[0074] As described above, the matching resistor 62B has the first capacitor 61C and the second capacitor 62D connected in series on both the power supply connection section 61A side and the high frequency signal input section 62A side, respectively, so that the DC component flowing through the matching resistor 62B is eliminated. Therefore, there is no need to consider the power consumption of the matching resistor 62B in the circuit design. As a result, the power efficiency is improved, the size of the matching resistor 62B can be physically reduced, a wiring circuit can be constructed using a pattern, and the high frequency characteristics are significantly improved.

[0075] figure 13 is As explained in Figure 12 This is a modified equivalent circuit diagram of the electro-optical conversion circuit 6 of the embodiment. The electro-optical conversion circuit 7 according to this modified example has the same basic configuration as the electro-optical conversion circuit 6. That is, the bias circuit is composed of a power supply connection unit 71A and a bias T circuit 71, and the bias T circuit 71 has an inductor 71B that is connected in series between the electro-optical conversion unit 72C and prevents a high-frequency signal from flowing from the high-frequency signal input unit 72A to the power supply connection unit 71A, and a first capacitor 71C that prevents a large direct current from flowing into the high-frequency signal input unit 72A. In addition, a matching resistor 72B is connected in parallel with the electro-optical conversion unit 72C between the high-frequency signal input unit 72A and the electro-optical conversion unit 72C to match the characteristic impedance of the high-frequency signal circuit with the electro-optical conversion unit 72C. In addition, since the matching resistor 72B is connected in series with the inductor 71B and the first capacitor 71C, a direct current is prevented from flowing from the power supply connection unit 71A. Furthermore, a second capacitor 72D is connected in series between the matching resistor 72B and the high frequency signal input section 72A. Even if a direct current is present in the high frequency signal input section 72A, the second capacitor 72D prevents the direct current from flowing through the matching resistor 72B.

[0076] In this modified example, a lead wire 71D for extracting a DC current is connected from the power supply connection portion 71A between the high frequency signal input portion 72A and the second capacitor 72D, so that a DC component is superimposed on the high frequency input from the high frequency signal input portion 72A.

[0077] In addition, The above As in the embodiment, As explained in Figs. 12 and 13 An optical data link having an optical transmission module equipped with the electrical-optical conversion circuit 6 or 7, and an optical transmission system capable of transmitting an optical signal from a transmitting device to a receiving device via the optical data link may be configured.

[0078] The technology disclosed in this specification is not limited to the above-mentioned embodiment. That is, it includes the embodiment shown as an example and the modification by a person skilled in the art based on them. It also includes the replacement or combination of parts or elements between one embodiment and another embodiment. Furthermore, the disclosed technical scope is not limited to the description of the embodiment. The disclosed technical scope is indicated by the description of the claims, and further includes all modifications within the meaning and scope equivalent to the description of the claims. [Explanation of symbols]

[0079] 1, 2 Optical transmission module 4 Optical Data Link 5 Optical Transmission Systems 11, 21 1st track 12, 22 Second track 13, 23 Joint 14, 24 High frequency signal input section 15, 25 End 16, 26 Power supply connection 17, 27 Electrical-optical conversion section 18, 28 Bypass capacitor 35 Microstrip Antenna

Claims

1. a first line having one end serving as a high-frequency signal input portion and the other end serving as a termination portion; a second line having an electro-optical conversion unit that converts an electrical signal input from the high frequency signal input unit into an optical signal and outputs the optical signal, and a power supply connection unit that is connected to a DC power supply and applies a voltage to drive the electro-optical conversion unit, each connected to one of both ends; a coupling section in which the first line and the second line are electromagnetically coupled to each other through a predetermined space and with a predetermined electrical length for a wavelength of a frequency used; having Depending on the frequency band of the device you are connecting to, In a frequency band range in which the attenuation of the coupling characteristic between the first line and the second line is smaller than the attenuation of the isolation characteristic, the second line is connected to the electrical-optical converter at one end in a forward propagating direction of a traveling wave of a high frequency signal input from the high frequency signal input unit to the first line, and is connected to the power supply connector at the other end; In a frequency band range in which the attenuation of the coupling characteristic between the first line and the second line is greater than the attenuation of the isolation characteristic, The second line is an optical transmission module in which the electrical-optical conversion unit is connected to one end in a direction propagating in the opposite direction to the traveling wave of the high frequency signal input from the high frequency signal input unit to the first line, and the power supply connection unit is connected to the other end.

2. 2. The optical transmission module according to claim 1, wherein the first line and the second line are formed of microstrip lines.

3. 2. The optical transmission module according to claim 1, wherein the first line and the second line are formed of coplanar lines.

4. a first dielectric substrate on one surface of which the first line is formed, and on a surface opposite to the surface on which the first line is formed, the high frequency signal input portion and the termination portion connected to the first line are disposed; a second dielectric substrate on one surface of which the second line is formed, and on a surface opposite to the surface on which the second line is formed, the power supply connection portion and the electro-optical conversion portion connected to the second line are disposed; 4. The optical transmission module according to claim 1, comprising a multilayer substrate in which a surface of the first dielectric substrate on which the first line is formed and a surface of the second dielectric substrate on which the second line is formed are arranged opposite each other, and a third dielectric substrate having a thickness that forms the coupling portion is interposed between the surface and a third dielectric substrate.

5. 3. The optical transmission module according to claim 2, having a four-layer structure composed of a second dielectric substrate on which the second line is formed, a first dielectric substrate on which the first line is formed, and an intermediate dielectric substrate on which a microstrip antenna is formed between the first dielectric substrate and the second dielectric substrate, wherein the microstrip antenna is disposed at an end position of the first line and is resonantly coupled with the second line at the predetermined electrical length to form the coupling portion.

6. The optical transmission module according to claim 1 , wherein the electrical length is λ / 4.

7. 7. The optical transmission module according to claim 1, wherein the termination portion is a characteristic impedance of each of the first line and the second line.

8. The optical transmission module according to claim 1 , wherein a photodiode is connected to the terminal portion as an optical-electrical conversion portion.

9. The optical transmission module according to claim 1 , wherein the electrical-optical conversion unit is a vertical-cavity surface-emitting laser.

10. The optical transmission module according to claim 1 , further comprising a bypass capacitor in a line connected to the power supply connection section.

11. a first line having one end connected to a high frequency signal input unit and the other end connected to an optical-electrical conversion unit; a second line having an electro-optical conversion unit that converts an electrical signal input from the high frequency signal input unit into an optical signal and outputs the optical signal, and a power supply connection unit that is connected to a DC power supply and applies a voltage to drive the electro-optical conversion unit, each connected to one of both ends; a coupling section in which the first line and the second line are electromagnetically coupled to each other through a predetermined space and with a predetermined electrical length for a wavelength of a frequency used; having Depending on the frequency band of the device you are connecting to, In a frequency band range in which the attenuation of the coupling characteristic between the first line and the second line is smaller than the attenuation of the isolation characteristic, the second line is connected to the electrical-optical converter at one end in a forward propagating direction of a traveling wave of a high frequency signal input from the high frequency signal input unit to the first line, and is connected to the power supply connector at the other end; In a frequency band range in which the attenuation of the coupling characteristic between the first line and the second line is greater than the attenuation of the isolation characteristic, The second line is an optical transmission module that connects the electrical-optical conversion unit to one end in a direction propagating in a reverse direction to a traveling wave of the high frequency signal input from the high frequency signal input unit to the first line, and connects the power supply connection unit to the other end; One or two optical cables connecting both ends of the optical transmission module; having An optical data link that enables bidirectional optical transmission, wherein each of the optical transmission modules connected to both ends is equipped with an electrical-to-optical conversion unit that outputs an optical signal to the optical cable and an optical-to-electrical conversion unit that inputs an optical signal from the optical cable.

12. 12. An optical transmission system capable of transmitting an optical signal from a transmitting device to a receiving device via the optical data link according to claim 11.

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