JP5492116B2 - Optical receiver module - Google Patents

Description

  The present invention relates to an optical receiver module, and more particularly to a high-frequency circuit included in an optical receiver module used in optical communication.

  An optical receiving module used for optical communication includes a light receiving element that photoelectrically converts incident signal light, an amplifier that amplifies an electric signal output from the light receiving element, and the like. A photodiode (PD) is generally used as a light receiving element.

  When converting a high-frequency signal having a band exceeding 10 Gbps, on-off modulation (ON / OFF keying) using a conventional intensity modulation method has low noise and flat frequency characteristics without oscillating up to a high-frequency region of 10 GHz or more. It is important to configure the optical receiving module to have Methods for improving the high-frequency characteristics are disclosed in, for example, the following documents.

  The optical signal receiving module disclosed in Patent Document 1 (Japanese Patent No. 4139594) has the following configuration. That is, the ground electrode of the amplifier is connected to the bias voltage input terminal of the light receiving element, and the chip carrier is not included in the path so that a current loop is formed between the light receiving element and the first stage transistor of the amplifier. Alternatively, a sub-ground electrode connected to the ground electrode via a capacitor having a predetermined capacity is provided in the amplifier. With this configuration, the electrical length of the current loop is shortened, so that it is possible to obtain an optical receiver module that can prevent oscillation due to noise and has excellent high-frequency characteristics.

  The optical receiver module disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 10-233741) has the following configuration. That is, a resonance circuit is configured by the coils provided on the anode electrode side and the cathode electrode side of the photodiode, the capacitance of the photodiode, and the like. The capacitance or the like compensates for a decrease in current amplitude frequency characteristic in a high frequency region. This makes it possible to obtain an optical receiver module with excellent high frequency characteristics.

  Patent Document 3 (Japanese Patent Laid-Open No. 2002-319698) discloses a photodiode having the following configuration. On the first conductive type semiconductor layer, a second conductive type semiconductor layer divided into a plurality by the first conductive type separation diffusion layer is laminated, and in the region of the adjacent second conductive type semiconductor layer, the light receiving element portion and the signal processing A circuit element portion is provided. One electrode of the light receiving element portion is provided on the lower surface of the first conductive type semiconductor layer, and the other electrode of the light receiving element portion is provided on the second conductive type semiconductor layer. With such a structure, the series resistance of the anode part of the photodiode is reduced, so that a photodiode with a high response speed can be realized.

Japanese Patent No. 4139594 Japanese Patent Laid-Open No. 10-233741 JP 2002-319698 A

  According to the configuration disclosed in Patent Document 1, oscillation can be prevented by shortening the electrical length of the loop formed by the PD and the amplifier. Further, according to the configurations disclosed in Patent Document 2 and Patent Document 3, the frequency characteristic of the gain can be flattened to a higher frequency, so that the optical reception module can receive a wideband signal.

  However, next-generation modulation schemes with excellent reception sensitivity, such as phase modulation schemes or digital coherent schemes, require output linearity and group delay characteristics in addition to the above characteristics. Further, in such a next-generation modulation system, balanced reception is performed in which a plurality of signal lights are received simultaneously, so that a multi-channel type optical receiver module having a plurality of light receiving units and a plurality of amplifiers is required. Thus, in the case of an optical receiver module having a plurality of light receiving units and a plurality of amplifiers, it is required to match the high frequency characteristics among a plurality of channels.

  In the conventional optical receiver module, when a flat frequency characteristic is to be obtained, the peripheral circuit of the PD element 1 is reflected by the reflection generated at the signal input electrode of the amplifier and the parasitic capacitance and parasitic inductance of the PD element or wiring. Unintentional resonance may occur with the amplifier. In this specification, “resonance” means a phenomenon in which a high-frequency signal having a specific frequency is confined.

  FIG. 11 is a diagram showing that a group delay is caused in the vicinity of a specific frequency when resonance occurs. FIG. 11 shows that a delay of group delay occurs at a frequency near 16 GHz. When resonance occurs, there arises a problem that the waveform of the signal output from the optical receiving module deteriorates.

  FIG. 12 is a schematic waveform diagram for explaining signal degradation due to resonance. FIG. 12A is a waveform diagram for explaining components of the input signal of the amplifier. As shown in FIG. 12A, the input signal includes a high frequency component W1 having a frequency near the resonance frequency and a high frequency component W2 having another frequency (a frequency lower than the resonance frequency). When resonance occurs, in the voltage signal output from the optical receiver module, a group delay difference occurs between a high frequency component having a frequency near the resonance frequency and a high frequency component having another frequency.

  FIG. 12B is a diagram schematically showing an eye pattern of the output signal of the optical receiving module when there is no group delay difference. FIG. 12C is a diagram schematically showing an eye pattern of the output signal of the optical receiving module when there is a group delay difference. As shown in FIGS. 12B and 12C, when a large resonance occurs, a high frequency component having a frequency close to the frequency of the resonance is optically received at a timing different from that of other high frequency components. Output from the module. Accordingly, as shown in FIG. 12C, the opening of the eye pattern is narrowed.

  The invention of Patent Document 1 (Japanese Patent No. 4139594) is directed to suppressing oscillation. That is, an object of the invention of Patent Document 1 is to prevent amplifier noise from being amplified by being input again to the amplifier via a current loop. For this reason, the invention of Patent Document 1 may not sufficiently prevent the above resonance.

  On the other hand, in the multi-channel module described above, due to the requirement of an optical system coupled to an optical fiber, it is necessary to arrange a plurality of light receiving portions close to each other at intervals of several hundred μm or less in the PD element. On the other hand, the wire length is limited in order to avoid a decrease in frequency characteristics due to the parasitic inductance of the wire. For this reason, a large number of amplifiers and chip capacitors must be mounted around the PD element.

  For this reason, it is difficult to use electrodes having the same shape or wiring having the same length in all channels. As shown in FIG. 13, when the lengths of the electrodes are different, there is a problem that a difference occurs in the frequency characteristics of the gain between the channels.

  An object of the present invention is to provide an optical receiver module having excellent frequency characteristics.

  In summary, the present invention is an optical receiver module, a light receiving element that converts signal light into an electrical signal when a bias voltage is applied, a voltage stabilizing circuit for suppressing fluctuations in the bias voltage, and a light receiving element. An amplifying circuit for amplifying the electric signal output from the signal line, and a resistor connected between the light receiving element and the voltage stabilizing circuit for attenuating the resonance caused by reflection occurring at the input end of the amplifying circuit.

  According to the present invention, an optical receiver module having excellent frequency characteristics can be realized.

It is a perspective view which shows the structure of the optical receiver module by Embodiment 1 of this invention. It is a top view of the optical receiver module shown in FIG. FIG. 3 is an equivalent circuit diagram of a portion corresponding to one channel of the optical receiver module according to Embodiment 1 of the present invention. 6 is a diagram showing a comparative example of the optical receiving module according to Embodiment 1. FIG. FIG. 5 is an equivalent circuit diagram of the optical receiver module shown in FIG. 4. FIG. 6 is a diagram showing a result of circuit simulation for determining the relationship between the group delay of the current input to the amplifier and the frequency for the configuration of the optical receiver module according to the first embodiment and the configuration of the comparative example. It is the figure which showed the measurement result of the frequency characteristic of the optical receiver module by Embodiment 1 of this invention. It is a perspective view which shows the structure of the optical receiver module by Embodiment 2 of this invention. It is a top view of the optical module shown in FIG. FIG. 6 is an equivalent circuit diagram of a portion corresponding to one channel of the optical receiver module according to the second embodiment of the present invention. It is the figure which showed that the delay of group delay arises in the vicinity of a specific frequency when resonance generate | occur | produces. It is a typical waveform diagram for demonstrating degradation of the signal by resonance. (A) is a wave form diagram for demonstrating the component of the input signal of amplifier. (B) is the figure which showed typically the eye pattern of the output signal of an optical receiver module in case there is no group delay difference. (C) is the figure which showed typically the eye pattern of the output signal of an optical receiver module in case there exists a group delay difference. It is a figure explaining the subject by the length of an electrode differing between several channels.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a perspective view showing a configuration of an optical receiver module according to Embodiment 1 of the present invention. FIG. 2 is a top view of the optical receiver module shown in FIG.

  With reference to FIG. 1 and FIG. 2, the optical receiving module 100 is configured as a four-channel optical receiving module and can receive four signal lights. However, the optical reception module according to Embodiment 1 may be configured as an optical reception module having more channels. The optical receiver module according to Embodiment 1 is used on the receiving side of an optical communication system and has a function of converting an optical signal input from an optical fiber (not shown) into an electrical signal.

  The optical receiving module 100 includes a PD element 1, amplifier ICs (Integrated Circuits) 2a and 2b, chip capacitors 3a to 3d, thin film resistor substrates 5a to 5d, wires 31a to 31d, 41a to 41d, and 42a to 42d. Have The PD element 1 and the amplifier ICs 2a and 2b are configured by a semiconductor chip. The amplifier ICs 2a and 2b function as an amplifier circuit that amplifies the electric signal from the PD element 1. The chip capacitors 3a to 3d function as a voltage stabilization circuit that suppresses fluctuations in the bias voltage. The thin film resistor substrates 5a to 5d function as resistors that attenuate resonance caused by reflection that occurs at the input ends of the amplifier circuits (amplifier ICs 2a and 2b).

  The amplifier ICs 2 a and 2 b are arranged on both sides of the PD element 1. That is, the amplifier IC 2 a faces the outer periphery 14 d of the PD element 1, and the amplifier IC 2 b faces the outer periphery 14 b of the PD element 1. The amplifier ICs 2a and 2b are arranged symmetrically with respect to the PD element 1.

  The thin film resistor substrates 5a and 5b and the chip capacitors 3a and 3b are disposed in the vicinity of the outer periphery 14a of the PD element 1 that is not opposed to the amplifier ICs 2a and 2b. Similarly, the thin film resistor substrates 5c and 5d and the chip capacitors 3c and 3d are disposed in the vicinity of the outer periphery 14c of the PD element 1 not facing the amplifier ICs 2a and 2b. The set of thin film resistor substrates 5 a and 5 b and chip capacitors 3 a and 3 b and the set of thin film resistor substrates 5 c and 5 d and chip capacitors 3 c and 3 d are arranged point-symmetrically with respect to the main surface of PD element 1.

  Note that the chip capacitors 3 a and 3 b are arranged outside the thin film resistor substrates 5 a and 5 b with respect to the PD element 1. The chip capacitors 3 c and 3 d are arranged outside the thin film resistor substrates 5 c and 5 d with respect to the PD element 1.

  The PD element 1 has four light receiving parts (11a to 11d). The light receiving portions 11a to 11d are formed in a row on the PD element 1 at a predetermined interval (for example, 100 μm to several hundred μm).

  The PD element 1 further includes anode electrodes 12a to 12d and cathode electrodes 13a to 13d. The cathode electrodes 13a to 13d are connected to the light receiving parts 11a to 11d, respectively. The cathode electrodes 13 a and 13 b have a pattern drawn from the corresponding light receiving portion to the vicinity of the outer periphery 14 a of the PD element 1. The cathode electrodes 13c and 13d have a pattern drawn from the corresponding light receiving portion to the vicinity of the outer periphery 14c of the PD element 1.

  The cathode electrode 13a is connected to the thin film resistor substrate 5a through the wire 41a. The thin film resistor substrate 5a is connected to the chip capacitor 3a through the wire 31a. Similarly, the cathode electrodes 13b to 13d are connected to the thin film resistor substrates 5b to 5d through wires 41b to 41d, respectively. The thin film resistor substrates 5b to 5d are connected to the chip capacitors 3b to 3d through wires 31b to 31d, respectively. A bias voltage is applied to each of the chip capacitors 3a to 3d.

  The anode electrodes 12a to 12d are connected to the light receiving portions 11a to 11d, respectively. The anode electrodes 12 a and 12 b have a linear pattern drawn from the corresponding light receiving portion to the outer periphery 14 b of the PD element 1. The anode electrodes 12 c and 12 d have a linear pattern drawn from the corresponding light receiving portion to the outer periphery 14 c of the PD element 1.

  Each of the amplifier ICs 2a and 2b is a differential amplifier and has two signal input electrodes. The anode electrodes 12a and 12b of the PD element 1 are connected to the signal input electrodes 21a and 21b of the amplifier IC 2a through wires 42a and 42b, respectively. The anode electrodes 12c and 12d of the PD element 1 are connected to signal input electrodes 21c and 21d of an amplifier IC 2b as an amplifier through wires 42c and 42d, respectively.

  FIG. 3 is an equivalent circuit diagram of a portion corresponding to one channel of the optical receiver module according to Embodiment 1 of the present invention. Referring to FIG. 3, cathode electrode 13a of PD element 1 is connected to thin film resistance substrate 5a as a resistance element via wire 41a. The thin film resistor substrate 5a is connected to the chip capacitor 3a through the wire 31a.

  A bias voltage (PD bias) supplied from the outside is applied to the cathode electrode 13a of the PD element 1 through the chip capacitor 3a, the wire 31a, the thin film resistor substrate 5a, and the wire 41a. The chip capacitor 3a functions as a bypass capacitor and functions to suppress noise caused by fluctuations in bias voltage.

  The light receiving unit 11a converts the incident signal light into a current signal. The current signal is output from the anode electrode 12a of the PD element 1 and input to the signal input electrode 21a of the amplifier IC 2a through the wire 42a. The current signal is converted into a voltage signal and amplified in the amplifier IC2a.

  The PD element 1, the amplifier IC 2a, the chip capacitor 3, and the thin film resistor substrate 5 are mounted on an element carrier 48 (not shown in FIGS. 1 and 2). The ground (GND) electrode 23 of the amplifier IC 2a is connected to the element carrier 48 via a wire 43a (not shown in FIGS. 1 and 2).

  Although not shown in FIGS. 1 and 2, wiring for supplying power to the amplifier ICs 2a and 2b and controlling the amplifier, wiring for outputting a voltage signal from the amplifier ICs 2a and 2b, and the like are provided in the optical receiving module. It is done.

  The thin film resistor substrate 5a is for attenuating resonance caused by reflection in both the signal input electrode 21a and the chip capacitor 3a of the amplifier IC 2a. The resistance value of the thin-film resistor substrate 5a is set sufficiently within a range that is sufficiently large to attenuate the resonance and that allows a decrease in the frequency characteristics of the PD element 1 due to an increase in series resistance. As will be described later, the resistance values of the thin film resistor substrates 5b and 5c are set larger than the resistance values of the thin film resistor substrates 5a and 5d.

  As shown in FIGS. 1 and 2, the configuration of the portions corresponding to each channel is the same as each other. In FIG. 3, the circuit configuration of the part related to the light receiving unit 11a is representatively shown as a part corresponding to one channel, but the circuit configuration of the part related to each of the light receiving units 11b to 11d is also shown in FIG. Same as the configuration. Therefore, detailed description of the circuit configuration of the portion corresponding to the remaining channels will not be repeated.

  When the electrical characteristics (for example, impedance, parasitic capacitance, parasitic inductance, electrical length, etc.) of the signal input unit of the amplifier IC 2a, the PD element 1, and the wires 31a, 41a, and 42a satisfy the reflection conditions, the periphery of the PD element 1 Resonance occurs between the circuit and the amplifier IC 2a. The reflection points in this case are considered to be the signal input electrode 21a and the chip capacitor 3a of the amplifier IC 2a. In Embodiment 1 of the present invention, a resistance element is inserted between the chip capacitor and the cathode electrode of the PD element. This can attenuate the resonance.

  In the first embodiment of the present invention, the resonance can be attenuated, so that the variation of the group delay characteristic can be suppressed. This point will be described based on a comparison between the optical receiving module according to the present embodiment and a comparative example thereof.

  FIG. 4 is a diagram showing a comparative example of the optical receiver module according to the first embodiment. FIG. 5 is an equivalent circuit diagram of the optical receiver module shown in FIG. With reference to FIGS. 4 and 5, the optical reception module 100 </ b> A includes a PD element 1, an amplifier IC 52, and a chip capacitor 3. The cathode electrode 13 of the PD element 1 is connected to the chip capacitor 3 through a wire 41. A bias voltage is applied to the chip capacitor 3 from the outside. Thereby, a bias voltage is applied to the cathode electrode 13 of the PD element 1.

  As understood from the comparison between FIG. 1 and FIG. 4, the optical receiving module 100 </ b> A differs greatly from the optical receiving module 100 according to the first embodiment in that a resistor (between the PD element 1 and the chip capacitor 3 is provided. The thin film resistor substrate is not provided. In the case of the optical receiving module 100A, only one light receiving unit is provided in the PD element 1, but a plurality of light receiving units may be provided in the PD element 1 in the configuration of FIG.

  Referring to FIG. 5, the anode electrode 12 of the PD element 1 is connected to the signal input electrode 21 of the amplifier IC 52 through the wire 42. The GND electrode 23 of the amplifier IC 52 is connected to the element carrier 48 through the wire 43. The signal output electrode 22 of the amplifier IC 52 is connected through a wire 44 to a high-frequency transmission path 45 patterned on the element carrier 48.

  The signal light incident on the light receiving unit 11 of the PD element 1 is converted into a current signal. The current signal is output from the anode electrode 12 of the PD element 1 and input to the signal input electrode 21 of the amplifier IC 52 through the wire 42. The current signal is converted into a voltage signal and amplified by the amplifier IC 52. The voltage signal is output from the signal output electrode 22 of the amplifier IC 52 to the outside of the module through the high-frequency transmission path 45.

  FIG. 6 is a diagram showing a result of circuit simulation for the relationship between the group delay of the current input to the amplifier and the frequency for the configuration of the optical receiver module according to the first embodiment and the configuration of the comparative example. is there. As shown in FIG. 6, in the case of the configuration of the comparative example, a group delay delay occurs in the vicinity of a specific frequency (about 16 GHz). In this case, there arises a problem that the waveform of the signal output from the optical receiving module deteriorates (see FIG. 12).

  On the other hand, in the configuration of the optical receiver module according to Embodiment 1 of the present invention, a resistance element is connected between the signal input electrode of the amplifier IC and the chip capacitor. As a result, resonance can be attenuated, so that fluctuations in group delay characteristics can be suppressed. Therefore, according to the first embodiment of the present invention, the group delay characteristic can be flattened.

  Here, a resistor for suppressing resonance where the input portion of the amplifier becomes a reflection point is generally connected to the input portion of the amplifier. However, when a resistor is connected to the input section of the amplifier, thermal noise is generated in the resistor due to a signal current flowing from the PD element to the amplifier IC. This thermal noise becomes noise and is further amplified by the amplifier IC.

  However, according to the first embodiment, the resistance element is not connected to the input part of the amplifier IC. Therefore, according to the first embodiment, not only can the resonance be attenuated, but also the generation of noise due to thermal noise can be prevented.

  Referring to FIGS. 1 and 2 again, cathode electrodes 13b and 13c are connected to light receiving portions 11b and 11c located inside light receiving portions 11a and 11d, respectively, in the vicinity of outer periphery 14a of PD element 1 and PD element 1 Each is pulled out to the vicinity of the outer periphery 14c. Therefore, the cathode electrodes 13b and 13c have a longer shape than the cathode electrodes 13a and 13d. The parasitic inductance increases as the electrodes become longer. Therefore, when a resistor is not connected to the cathode electrode of the PD element 1 as in the configuration of the comparative example, peaking occurs more strongly in the frequency characteristic of the gain. FIG. 13 shows an example of peaking. When the electrodes are long, the gain (S21 parameter) increases near the frequency of 15 to 20 GHz, and the gain decreases sharply at a frequency of 20 GHz or more.

  On the other hand, according to the first embodiment, a resistor is connected in series with the PD element. The larger the resistance value of the resistor, the lower the frequency characteristics. In the first embodiment, an appropriate difference is provided in the resistance values of the thin film resistor substrates 5a to 5d in accordance with the difference in inductance between the cathode electrodes 13a to 13d. Thereby, the frequency characteristics in each channel can be substantially matched. Specifically, when the parasitic inductances of the two cathode electrodes are different, the resistance value of the resistor connected to the cathode electrode having the larger parasitic inductance is set as the resistance value connected to the cathode electrode having the smaller parasitic inductance. Larger than the resistance value. Thereby, in the optical receiver module having a plurality of channels, the frequency characteristics in each channel can be substantially matched.

  More specifically, when the two cathode electrodes have different lengths, the resistance value of the thin film resistor substrate connected to the longer cathode electrode is changed to the resistance value of the thin film resistor substrate connected to the shorter cathode electrode. Make it bigger. Therefore, the resistance values of the thin film resistor substrates 5b and 5c are set larger than the resistance values of the thin film resistor substrates 5a and 5d. Since the parasitic inductance of the longer cathode electrode is larger than the parasitic inductance of the shorter cathode electrode, the frequency characteristics in each channel can be made to substantially match by making the resistance values different as described above.

  FIG. 7 is a diagram showing measurement results of frequency characteristics of the optical receiver module according to Embodiment 1 of the present invention. Referring to FIG. 7, the vertical axis of the graph indicates the S parameter (S21), and the horizontal axis of the graph indicates the frequency. In this measurement, an optical fiber for inputting signal light to the PD element was input, and a high frequency output terminal of the optical receiving module was output. The calibrated optical modulator was connected to the network analyzer, and the S21 parameter was measured by comparing the input light power and the output power. Two curves A and B show frequency characteristics respectively corresponding to two modules having different cathode electrode lengths. FIG. 7 shows that the frequency characteristics of the respective channels can be matched by providing an appropriate difference in the resistance value of the thin film resistor.

  As described above, according to the first embodiment, resonance in the optical receiving module can be suppressed. Furthermore, according to the first embodiment, by adjusting the resistance value of the thin film resistor in advance, in the optical receiver module having a plurality of channels, the frequency characteristics of each channel can be aligned.

  Further, in the first embodiment, a plurality of amplifier ICs are arranged symmetrically around the PD element, and a plurality of chip capacitors and a plurality of resistance elements (thin film resistor substrates 5a to 5d) are also arranged symmetrically around the PD element. The arrangement direction of the plurality of chip capacitors and the plurality of resistance elements is different from the arrangement direction of the plurality of amplifier ICs. With such a configuration, the light receiving portions of the modules corresponding to the respective channels can be disposed close to each other, so that the optical paths of the plurality of signal lights can be accommodated in the effective system of the coupling optical system. Therefore, it is possible to couple a plurality of signal lights to a plurality of light receiving parts using one optical system.

[Embodiment 2]
FIG. 8 is a perspective view showing a configuration of an optical receiver module according to Embodiment 2 of the present invention. Referring to FIGS. 1 and 8, the optical receiver module 101 according to the second embodiment uses thin film resistor pattern portions 15a to 15d formed on the cathode electrodes 13a to 13d as resistance instead of the thin film resistor substrates 5a to 5d. It differs from the optical receiving module 100 according to the first embodiment in that it has an element.

  FIG. 9 is a top view of the optical module shown in FIG. Referring to FIGS. 8 and 9, in optical receiver module 101 according to the second embodiment, thin film resistor substrates 5a to 5d and wires 31a to 31d are omitted. Further, chip capacitors 3a to 3d are connected to cathode electrodes 13a to 13d via wires 41a to 41d, respectively.

  The thin film resistance pattern portions 15a to 15d are provided in the middle of the cathode electrodes 13a to 13d, respectively. The resistance value of the thin-film resistance pattern portion 15a is larger than the resistance value of other portions of the cathode electrode 13a. The resistance value of each of the thin film resistance pattern portions 15b to 15d is also larger than the resistance value of the other part of the corresponding cathode electrode. For example, the pattern of the cathode electrode is divided into a portion connecting the wire and a portion connected to the light receiving portion, and the space between these portions is replaced with a pattern of a material having a high resistivity. The resistance values of the thin-film resistance pattern portions 15b and 15c are determined to be larger than the resistance values of the thin-film resistance pattern portions 15a and 15d.

  Since the configuration of other parts of optical receiving module 101 is the same as the configuration of the corresponding part of optical receiving module 100 according to Embodiment 1, detailed description thereof will not be repeated.

  FIG. 10 is an equivalent circuit diagram of a portion corresponding to one channel of the optical receiver module according to the second embodiment of the present invention. Referring to FIGS. 3 and 10, the circuit configuration of the optical receiver module according to the second embodiment of the present invention is the same as the circuit configuration of the optical receiver module according to the first embodiment of the present invention.

  Similar to the first embodiment, in the second embodiment, a resistor is connected in series between the cathode of the PD element and the capacitor. Therefore, it is possible to attenuate the resonance caused by reflection at both the input part of the amplifier IC and the capacitor.

  Further, according to the second embodiment, by providing an appropriate difference in the resistance value of the thin film resistor pattern according to the inductance of the cathode electrode, the frequency characteristics of the modules corresponding to the respective channels can be matched. Therefore, as in the first embodiment, the light receiving portions of the modules corresponding to the respective channels can be arranged close to each other. Therefore, it is possible to couple a plurality of signal lights to a plurality of light receiving sections using one optical system.

  Furthermore, according to the second embodiment, the length of the electrode connecting the capacitor and the light receiving unit is reduced as compared with the first embodiment. Therefore, according to the second embodiment, the parasitic inductance existing from the light receiving unit to the capacitor can be reduced as compared with the first embodiment, so that the frequency characteristics can be further flattened.

  In each of the above embodiments, an optical receiver module having a plurality of channels is shown. However, the present invention can also be applied to an optical receiver module having a single channel.

  In addition, the plurality of light receiving units are not limited to be arranged one-dimensionally, and may be arranged two-dimensionally. Also in this case, the length of the electrode connected to the cathode of each light receiving unit may be different. Therefore, by appropriately adjusting the resistance value of the resistance element, the frequency characteristics of the modules corresponding to the respective channels can be matched.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 PD element, 2a, 2b, 52 Amplifier IC, 3, 3a-3d Chip capacitor, 5, 5a-5d Thin film resistive substrate, 11, 11a-11d Light-receiving part, 12, 12a-12d Anode electrode, 13, 13a-13d Cathode electrode, 14a-14d outer periphery, 15a-15d thin film resistor pattern part, 21, 21a-21d signal input electrode, 22 signal output electrode, 23 ground electrode, 31a-31d, 41a-41d, 42a-42d, 41-44 wire , 45 High-frequency transmission line, 48 element carrier, 100, 100A, 101 optical receiver module, A, B curve, W1, W2 high-frequency component.

Claims (4)

A light receiving element that converts signal light into an electrical signal by applying a bias voltage;
A voltage stabilizing circuit for suppressing fluctuations in the bias voltage;
An amplification circuit for amplifying the electrical signal output from the light receiving element;
Is connected between the voltage stabilization circuit and the light receiving element, Bei example a resistor for attenuating the resonance by reflection caused by the input of the amplifier circuit,
The light receiving element includes a plurality of light receiving units each converting signal light into an electrical signal,
A plurality of electrodes respectively connected to the plurality of light receiving units;
The resistor includes a plurality of resistance elements respectively connected to the plurality of electrodes,
The resistance value of each of the plurality of resistance elements is determined according to the parasitic inductance of the corresponding electrode among the plurality of electrodes so that the frequency characteristics of the plurality of light receiving units match.
The optical receiver module , wherein the resistance value of each of the plurality of resistance elements is set such that the resistance value increases as the parasitic inductance increases between the plurality of resistance elements . The plurality of light receiving units are arranged along at least one direction,
The optical receiving module according to claim 1 , wherein the resistance values of the plurality of resistance elements are determined such that the longer the electrode is, the larger the resistance value is. The voltage stabilization circuit includes a plurality of capacitors respectively connected to the plurality of resistance elements,
The amplifier circuit includes a plurality of amplifiers arranged point-symmetrically across the light receiving element,
The optical receiver module according to claim 2 , wherein the plurality of capacitors are arranged point-symmetrically across the light receiving element so as to be along a direction different from an arrangement direction of the plurality of amplifiers. The optical receiving module according to claim 2 , wherein each of the plurality of resistance elements is formed as a part of the corresponding electrode.

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