JP2009244833A - Optical receiver with built-in variable optical attenuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical receiver with built-in variable optical attenuator, capable of performing high speed adjustment of optical attenuation quantity while reducing the size. <P>SOLUTION: The optical receiver 100 with a built-in variable attenuator 102 comprises a condenser lens 104 collecting incident light from an optical fiber 120, and a light receiving element 106 receiving incident light from the condenser lens 104. The condenser lens 104 is disposed to form a convergence optical system within an MSA package 110, and the variable attenuator 102 is configured to adjust the attenuation quantity of the light received by the light receiving element 106 by changing the optical path of the incident light from the optical fiber 120. By using the convergence optical system, the size of the optical receiver can be reduced, compared with a conventional collimate system, and the variable optical attenuator such as a magnetic optical element or an MEMS element capable of adjusting the optical attenuation quantity at high speed can be contained within the de facto MSA package made of the optical receiver. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical receiver incorporating a variable optical attenuator. In particular, the present invention relates to an optical receiver including a variable optical attenuator that can be miniaturized and can adjust an optical attenuation amount at high speed.

  Optical receivers used in conventional optical communication networks have been developed with the theme of improving reception sensitivity in order to realize a longer transmission distance. In particular, a light receiving element called an avalanche photodiode (APD) that photoelectrically converts minute signal light and receives the amplified signal light is suitable for receiving minute signal light. However, the APD has a problem that when a relatively strong signal light is incident, the noise of the received signal increases, and in some cases, the receiver is broken, that is, the overload resistance is low.

  Actually, in order to avoid APD breakdown, a variable optical attenuator (VOA) is mounted in the APD receiver, and when strong signal light is incident, the VOA moderately attenuates the intensity of the signal light. A VOA built-in APD receiver that realizes a good reception state has also been developed (Non-patent Document 1). This VOA uses a bimetal used for a thermostat so that the plate blocks the optical path. However, the VOA built-in APD receiver that can be procured at present cannot adjust the optical attenuation amount of the built-in VOA element at high speed, and it takes about 50 msec for the adjustment.

  On the other hand, VOA elements that can adjust the attenuation amount at a high speed of about 1 to several msec include those using a micromachine (MEMS) (Non-Patent Documents 2 and 3), and those using a magneto-optical element (Non-Patent Document 4). There is. However, these VOAs are large in size and cannot be accommodated in a de facto optical receiver package called 10 Gigabit-Per-Second Surface-Mount Receiver multi-source agreement (MSA), as shown in FIG. there were. Therefore, it is necessary to connect the APD receiver and the VOA element using an optical fiber externally, which causes an increase in the size and cost of an optical receiver or an optical transceiver that must adjust the optical attenuation amount at high speed. It was. The MSA package shown in FIG. 1 has a width (W) of 8.0 mm, a length (L) of 8.75 mm, and a height (H) of 5.0 mm at the maximum.

Eudyna, “10 Gbit / s Receivers with VOA,” [online], [searched February 21, 2008], Internet <URL: http://www.us.eudyna.com/j/products/newproducts/10gbits_receiver_with_voa .html> Enomoto and three others, “Device packaging technology for MEMS optical variable attenuators”, Journal of Japan Institute of Electronics Packaging, Vol. 9, no. 4, 2006, pp. 235-239 Morimoto and three others, “Development of MEMS-type variable optical attenuators”, Furukawa Electric Times, No. 111, pp. 25-30 Furukawa Electric, “Variable Optical Attenuator”, [online], [Search February 21, 2008], Internet <URL: http://www.fdk.co.jp/cyber-j/pi_opt_voa.htm>

  At present, the capacity of optical communication networks is being increased by adopting wavelength division multiplexing transmission systems and wavelength routing mechanisms. In next-generation optical networks, the path of signal light incident on the receiver is switched quickly (several msec). Therefore, an optical receiver for a next-generation optical network is required to have a built-in high-speed signal light intensity adjustment function of about 1 msec.

  The present invention has been made in view of the above problems in such a situation, and an object of the present invention is to incorporate a variable optical attenuator that can be miniaturized and can adjust the optical attenuation amount at high speed. An optical receiver is provided.

  In order to achieve the above object, the present invention provides an optical receiver including a variable attenuator, and a condensing lens for condensing incident light from an optical fiber. A light receiving element that receives incident light from the condenser lens, the condenser lens is disposed so as to form a converging optical system, and the variable attenuator changes the optical path of the incident light to change the optical path. The light-receiving element is configured to adjust the attenuation amount of light received.

  The invention according to claim 2 is the optical receiver according to claim 1, further comprising an optical aperture between the condenser lens and the light receiving element.

  The invention described in claim 3 is the optical receiver described in claim 1 or 2, characterized in that the variable attenuator is located on the incident side of the condenser lens.

  The invention according to claim 4 is the optical receiver according to any one of claims 1 to 3, wherein the variable attenuator is located on an exit side of the condenser lens. .

  The invention according to claim 5 is the optical receiver according to any one of claims 1 to 4, wherein the variable attenuator is composed of a magneto-optical element.

  According to a sixth aspect of the present invention, there is provided the optical receiver according to any one of the first to fourth aspects, wherein the variable attenuator is composed of a transmissive MEMS element.

  The invention according to claim 7 is the optical receiver according to any one of claims 1 to 6, wherein the light receiving element is an avalanche photodiode.

  The invention according to claim 8 is the optical receiver according to any one of claims 1 to 7, wherein the condenser lens and the light receiving element have an imaging magnification in the range of 1 to 5. It is comprised so that it may become.

  The invention according to claim 9 is the optical receiver according to any one of claims 1 to 8, further comprising temperature adjusting means.

  According to a tenth aspect of the present invention, there is provided the optical receiver according to any one of the first to ninth aspects, wherein the optical receiver is accommodated in an MSA package.

  According to the present invention, the variable optical attenuator (VOA) can be downsized. In addition, since a high-speed variable optical attenuator can be used, both high-speed adjustment of optical attenuation and miniaturization can be achieved. Thereby, the performance improvement and cost reduction of the optical receiver incorporating the variable optical attenuator can be realized.

  Specifically, by using the converging optical system, the shift amount of the light beam necessary for attenuation is reduced, and the VOA can be downsized. Further, unlike the collimating optical system, the converging optical system does not require a collimating lens. Further, since the shift amount of the light beam can be reduced by using the optical diaphragm, it contributes not only to further miniaturization of the VOA but also to reduction of electric power supplied to the VOA, which is effective from the viewpoint of energy saving.

  Further, according to the present invention, since the optical receiver incorporating the variable optical attenuator can be accommodated in the same size package as the conventional optical receiver, the optical transceiver is maintained while maintaining compatibility with the conventional optical receiver. Can be reduced in size and cost.

  VOA elements that can adjust the amount of attenuation at high speed include those using silicon MEMS (Si-MEMS) and magneto-optical elements, but these elements are large in size, and MSA optical receiver packages include: Cannot be accommodated. One of the reasons why the size is increased is that a collimating optical system is used. In the case of a collimating optical system, since the signal light becomes a parallel light beam, there is an advantage that the optical path length can be arbitrarily designed. However, in the collimating optical system, the signal light emitted from the optical fiber must be collimated through a collimating lens to be a collimated light beam, and then collimated light must be collected through the condenser lens and incident on the light receiving element. No. Therefore, in the collimating optical system, not only the space required for the VOA, but also the collimating lens installation space for converting the emitted light from the optical fiber into collimated light and the collimated light transmitted through the VOA are collected and incident on the light receiving element. It is necessary to install a condensing lens for this purpose.

  Further, when a VOA of a type that attenuates signal light by shifting the signal light beam in parallel without changing the traveling direction of the signal light, such as a magneto-optical element or a transmissive MEMS element, is used in the collimating optical system, FIG. As shown in FIG. 3, the signal light received by the light receiving element 12 cannot be attenuated unless the beam is shifted outside the numerical aperture NA (˜1 mm) of the condenser lens 10. Therefore, a shift amount ΔX of about the beam diameter of signal light (usually several hundred μm) is necessary, and the VOA element 14 is inevitably increased in size. Therefore, in a collimating optical system, it is difficult to realize a small optical receiver with a variable optical attenuator using a magneto-optical element and a transmission type Si-MEMS element that are effective as VOAs capable of adjusting the attenuation amount at high speed.

  On the other hand, as shown in FIG. 3, when a converging optical system is used, a small parallel shift amount (ΔX) within the numerical aperture NA of the condenser lens 20 can be expanded to n × ΔX by the imaging magnification n of the optical system. Therefore, the parallel shift amount necessary for the attenuation of the signal light may be 1 / n of the light receiving diameter of the light receiving element 22. Here, the imaging magnification n of the optical system is the focal length of the condensing lens, the position of the lens in the optical system (the distance between the VOA 24 and the condensing lens 20, the distance between the condensing lens 20 and the light receiving element 22). Distance).

  The light receiving diameter of a general APD in 10G class optical communication is 25 μm. If the imaging magnification of the optical system is n = 2.5, the shift amount of the light beam necessary for the attenuation of the signal light is 25 / 2.5 = 10 μm, which is a shift of 1/10 or less compared to the collimating optical system. You can see that the amount is good. Further, unlike the collimating optical system, the converging optical system is not necessary for a collimating lens, which is advantageous for downsizing.

  FIG. 4 shows how the signal light is attenuated by the shift of the signal light in the converging optical system. In FIG. 4A, all of the signal light 30 is incident on the light receiving surface 34 of the light receiving element 32, and almost 100% of the signal light is received. On the other hand, in FIG. 4B, a part of the signal light 30 protrudes from the light receiving surface 34 of the light receiving element 32, and the signal light is attenuated. Thus, by shifting the beam of signal light, the signal light can be attenuated by the converging optical system.

  In FIG. 3, the optical beam shift amount can be further reduced by inserting an optical aperture between the VOA 24 and the light receiving element 22 to the same extent as the light receiving diameter of the light receiving element. That is, by making the light receiving diameter of the light receiving element 22 appear small when viewed from the VOA 24 by the optical diaphragm, the light beam shift required for obtaining a predetermined attenuation amount by effectively reducing the light receiving diameter. The amount can be reduced. This reduction of the shift amount contributes not only to the miniaturization of the magneto-optical element and the transmissive Si-MEMS element used as the VOA but also to the reduction of power supplied to the VOA element, and is effective from the viewpoint of energy saving.

  In the present invention, a high-speed VOA function and miniaturization can be realized at the same time by using a magneto-optical element and a transmissive Si-MEMS element capable of high-speed attenuation adjustment in a converging optical system. Further, an optical diaphragm can be inserted between the VOA and the light receiving element, and further miniaturization and energy saving can be realized. In addition, the developed small VOA can be mounted in an MSA optical receiver package, and a VOA built-in optical receiver compatible with a normal MSA optical receiver can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In these embodiments, APD is described as an example of the light receiving element, but other light receiving elements such as a pin photodiode (PD) element and an MSM element may be used.

(First embodiment)
FIG. 5 is a side view showing a partially cutaway APD receiver with built-in VOA according to the first embodiment of the present invention. The receiver 100 accommodates a VOA 102 using a magneto-optical element, a condensing lens 104 fixed in a V-groove, and a light receiving element 106 mounted on a subcarrier in an MSA package 110. The receiver 100 further accommodates electrical circuit components 108 such as a transimpedance amplifier (TIA), a chip resistor and a chip capacitor in the MSA package 110.

  In this embodiment, a converging optical system is used, and the imaging magnification is designed to be 2.2 times. Further, a magneto-optical element was used as the VOA 102, and an APD element having a light receiving diameter of 25 μm was used as the light receiving element 106. The size of this magneto-optical element is 3 mm in length, 4 mm in width, and 3 mm in thickness.

  In order to assemble this receiver, first, the above components are mounted in a package, and terminals that need to be connected are connected by wire bonding. Next, the package lid is welded and hermetically sealed in a nitrogen atmosphere. Thereafter, a leak check for hermetic sealing is performed.

  After the receiver is assembled, the alignment process is performed. In FIG. 6, a receiver package 110 is attached to an alignment device (not shown) together with an optical fiber 120, a housing 130, and a housing 140. Next, the optical connector 150 of the optical fiber 120 is connected to the laser module 160, and light having a predetermined intensity is incident on the optical fiber 120. An ammeter 170 is connected to the lead 112 of the package connected to the APD, and the positions of the optical fiber 120, the housing 130, and the housing 140 are adjusted so that the light receiving current of the APD is maximized. Then, using the YAG laser, the optical fiber 120, the casing 130, and the casing 140 are welded and fixed at the position.

  In a state where the magneto-optical element 102 is not energized, the signal light enlarged to a diameter of 22 μm is incident on almost the center of the light receiving portion of the APD 106, and almost 100% of the signal light is received. When a current is passed through the magneto-optical element 102, the light beam incident on the condensing lens 104 is shifted in parallel according to the amount of the current, and a signal is shifted to a position shifted on the APD 106 by about 2.3 times the parallel shift amount. Light enters. Therefore, when the shift amount exceeds 1 μm, the signal light beam protrudes from the light receiving portion of the APD 106, and the reception signal is attenuated. This attenuation amount (that is, the shift amount) can be controlled at high speed and precisely by the current value of the magneto-optical element, and the magneto-optical element functions as a variable optical attenuator that responds at high speed.

  The amount of shift of the light beam at the light receiving element by the VOA is effective within 50 μm considering the light receiving diameter of the light receiving element. This shift amount is equal to a value obtained by dividing the light receiving diameter of the APD element by the imaging magnification. Accordingly, considering that the light receiving diameter of the APD element is about 10 to 50 μm, the imaging magnification is 1 or more and 5 or less. Further, considering that the light receiving diameter of a commonly used APD element is about 20 to 30 μm, the imaging magnification is 1.5 to 2.5.

  Next, optical attenuation characteristics of the VOA part in the manufactured VOA built-in APD receiver will be described. 0.2 mW CW light (DC light or unmodulated light) was incident on the VOA built-in APD receiver, and the light receiving current of the APD element was measured. At this time, a voltage of 10 V is applied to the APD element so that the multiplication factor (M value) is 1. When the M value = 1, since the photoelectric conversion efficiency of the APD element is about 0.9 A / W, the measured light receiving current value is about 180 μA. Subsequently, in order to attenuate the incident light intensity, a change in the received light current value was measured while applying a voltage to the VOA portion. FIG. 7 shows a result plotted in decibels with the ratio of the received light current value measured at each applied voltage and the received light current value at no voltage (180 μA) as an attenuation amount. As the voltage applied to the VOA portion increases, the light receiving current value decreases, and when 1 V is applied, the phenomenon reaches 18 μA, which is 1/10 of no voltage (FIG. 7: −10 dB). Furthermore, when the applied voltage of VOA is increased to 1.4V, the light receiving current decreases to 0.57 μA (FIG. 7: −25 dB). This attenuation amount protects the APD element and obtains a good reception state. Therefore, the practically sufficient attenuation was obtained. Further, when 1.4 V is applied (at -25 dB), the value of the current flowing through the VOA element is 44 mA, and the power consumption is as extremely small as 60 mW. This reduction in power consumption is brought about by a reduction in the amount of optical path shift by the convergence optical system of the present invention, indicating the effectiveness of the present invention in reducing power consumption.

Next, the performance of the manufactured VOA built-in APD receiver 100 will be described. Connect the optical connector 150 of the receiver to the laser module 160 modulates the extinction ratio 10dB with a modulation signal of NRZ-PRBS23 ^-1 of 10.7 Gbit / s, and measuring characteristics of the bit error rate (BER characteristics). FIG. 8 shows the result. In the figure, the solid line (a) is the BER characteristic when the VOA is not energized (maximum transmittance), and the dotted line (b) is the BER characteristic when 1.0 V is applied to the VOA (when the attenuation is 10 dB). It is. In the solid line (a), a code error due to overload occurs in the vicinity of the average received light intensity of −5 dBm, as in a normal APD receiver. On the other hand, in the dotted line (b), due to the attenuation of the received light intensity due to the VOA, the occurrence of a code error due to overload is shifted to the high light intensity side up to around +5 dBm. This result shows that the variable dynamic attenuation of 0 to 10 dB by the VOA can increase the reception dynamic range of the APD element: 22 dB (−27 dBm to −5 dBm) to 32 dB (−27 dBm to +5 dBm) by 10 dB.

  Here, the 10 dB expansion of the receiving dynamic range has been described by taking the case where the applied voltage range of the VOA is 0 to 1.0 V as an example based on FIG. 8, but by expanding the variable range of the applied voltage to 0 to 1.4 V. It is clear from the results of FIG. 7 that the reception dynamic range can be expanded by 25 dB.

  Next, the response speed of the VOA optical attenuation to the electrical signal was evaluated. In this evaluation, in order to eliminate the influence of the response speed of the transimpedance amplifier (TIA), a sample which is not mounted with TIA but wire-bonded so that a photocurrent signal from the APD can be directly taken out was used.

  FIG. 9 shows a result of observing simultaneously an input electric signal (1) to the VOA and a photocurrent signal (2) from the APD with an oscilloscope. The electric signal (1) in the figure is a 10 kHz square wave, and one horizontal axis of the oscilloscope corresponds to 50 μsec. From FIG. 9, it can be seen that the change in the photocurrent intensity (2) sufficiently follows the change in the electrical signal (1). The response time of the VOA read from the rise (20 → 80% of the amplitude) and the fall (80 → 20% of the amplitude) of the photocurrent intensity (2) is 7 μsec, and the response time of the conventional VOA is several msec. A high-speed response close to 1/1000 is realized.

  Furthermore, a receiver in which a temperature controller (heater or thermoelectric cooler) is mounted below the VOA of the VOA built-in APD receiver was manufactured. Comparison was made between the receiver with temperature control function and a combination of a conventional receiver and a VOA. Specifically, the relationship between the light attenuation and the ambient temperature was measured by changing the ambient temperature while keeping the applied current of VOA constant at 40 mA. FIG. 10 shows the result. In the figure, a white circle is a case where the temperature of the VOA section is maintained at 45 ° C. with a receiver having a temperature adjustment function, and a black circle is a case where a conventional receiver and VOA are combined (no temperature adjustment). In the white circle, the attenuation is stable regardless of the ambient temperature, but in the black circle, the attenuation is reduced at high temperatures. Thus, the performance can be further improved by adding the temperature control function.

(Second Embodiment)
FIG. 11 is a partially cutaway side view showing a VOA built-in APD receiver according to a second embodiment of the present invention. This receiver 200 includes a VOA 202 using a Si-MEMS element, a condensing lens 204 fixed to a V-groove, an optical diaphragm 205 having a pinhole in a silicon plate (Si plate), and a subcarrier. The mounted light receiving element 206 is accommodated in the MSA package 210. The receiver 200 also houses electrical circuit components 208 such as a transimpedance amplifier (TIA), chip resistors and chip capacitors in the MSA package 210.

  In this embodiment, a converging optical system is used, and the imaging magnification is designed to be 2.0 times. Further, a transmissive Si-MEMS element was used as the VOA 202, and an APD element having a light receiving diameter of 25 μm was used as the light receiving element 206. The size of this Si-MEMS element is 3 mm in length, 4 mm in width, and 1 mm in thickness. Further, a Si plate with a pinhole having a diameter of 50 μm was used as the optical diaphragm 205.

  To assemble this receiver, first, the above components are mounted in a package. Specifically, since the imaging magnification of this optical system is designed to be 2.0 times, emitted light having a beam diameter of 10 μm emitted from the optical fiber is incident on the APD light receiving surface with a beam diameter of 20 μm which is about twice as large. Thus, the positions of the condenser lens 204, the VOA 202, the optical diaphragm 205, and the APD 206 are determined. At this time, the beam diameter at the optical diaphragm 205 is set to about 40 μm.

  After mounting the parts, the terminals that need to be connected are connected by wire bonding. Next, the package lid is welded and hermetically sealed in a nitrogen atmosphere. Thereafter, a leak check for hermetic sealing is performed. After the receiver is assembled, the alignment process is performed as in the case of the first embodiment.

  The Si-MEMS element used in this embodiment is a transmissive type and functions as a VOA by the following mechanism. The Si-MEMS element has a Si plate that is inclined by electrostatic force when a voltage is applied. The Si plate is coated with an antireflection film, and is placed so that the Si plate is perpendicular to the optical axis of the signal light when no voltage is applied. For this reason, in the non-energized state, the signal light beam does not shift, and the signal light enters almost the center of the light receiving portion of the APD element. When a voltage is applied to the Si-MEMS element to energize it, the Si plate is tilted and signal light is incident at an angle corresponding to the tilt of the Si plate. At this time, due to the refractive index difference between air and Si, the signal light is refracted at the air / Si interface and the optical path is bent. Furthermore, when signal light is emitted from the Si plate into the air, refraction opposite to that at the time of incidence occurs at the Si / air interface, and the optical path returns to the original angle. However, since the light propagates through the Si plate at an angle different from that of air, the signal light is shifted in a direction perpendicular to the incident optical path. The incident position of the signal light on the APD is also shifted in accordance with the shift amount, and the received light amount of the APD can be varied. This shift amount can be controlled by controlling the tilt angle of the Si plate with the voltage applied to the Si-MEMS element, thereby realizing the VOA function.

Next, the performance of the manufactured VOA built-in APD receiver will be described. Similarly to the case of the first embodiment, the optical connector of the receiver 200 is connected to the laser module, and the signal is modulated to an extinction ratio of 10 dB with a 10.7 Gbit / s NRZ-PRBS2 ³¹ −1 modulation signal. Rate characteristics (BER characteristics) were measured. FIG. 11 shows the result. In the figure, the solid line (a) is the BER characteristic when the VOA is not energized (maximum transmittance), and the dotted line (b) is the BER characteristic when the VOA is 15 V (minimum transmittance). The dotted line (b) is shifted to the 20 dBm high light intensity side compared to the solid line (a). That is, it can be seen that the maximum amount of attenuation of the VOA is 20 dB, and the attenuation performance is equivalent to the case where the conventional optical receiver and the variable optical attenuator are combined.

  Also, the response speed of the VOA was evaluated by the same method as in FIG. 9 of the first embodiment, and as a result, it was confirmed that a high-speed response of about 0.5 msec was obtained. This response speed is about 1/10 of the response speed of the conventional Si-MEMS type VOA element of 5 to 10 msec, which is a practically sufficient response speed. This increase in speed is an effect of reducing the tilt angle of the Si plate of the Si-MEMS element necessary for light attenuation by the optical diaphragm 205, and shows the effectiveness of the present invention.

  The present invention has been described above with respect to several embodiments. However, in view of the many possible embodiments to which the principles of the present invention can be applied, the embodiments described herein are merely illustrative, It is not intended to limit the scope of the invention. For example, the optical aperture used in the second embodiment may be used in the first embodiment. In the first embodiment, the condensing lens 102 is arranged behind the VOA 102. However, the condensing lens 102 may be arranged in front of the VOA 102 as in the second embodiment. Conversely, in the second embodiment, the condensing lens 204 is disposed in front of the VOA 202, but the condensing lens 204 may be disposed behind the VOA 202 as in the first embodiment. . As described above, the configuration and details of the embodiment exemplified here can be changed without departing from the gist of the present invention. Further, the illustrative components and procedures may be changed, supplemented, or changed in order without departing from the spirit of the invention.

It is a perspective view of the MSA package used for the conventional optical receiver. It is a figure explaining the principle of the variable optical attenuator in a collimating optical system. It is a figure explaining the principle of the variable optical attenuator in a convergence optical system. It is a figure which shows a mode that signal light shifts from the light-receiving surface of a light receiving element in a convergence optical system. It is a side view which shows a partially broken optical receiver with a built-in variable attenuator according to the first embodiment of the present invention. It is a figure for demonstrating the alignment process of the optical receiver with a built-in variable attenuator. It is a figure which shows the relationship between the optical attenuation amount of the optical receiver with a built-in variable attenuator which concerns on the 1st Embodiment of this invention, and the voltage applied to the variable optical attenuator. It is a figure which shows the characteristic of the code error rate of the optical receiver with a built-in variable attenuator which concerns on the 1st Embodiment of this invention. It is a figure which shows the response characteristic of the optical receiver with a built-in variable attenuator which concerns on the 1st Embodiment of this invention. It is a figure which shows the temperature characteristic of the optical receiver with a built-in variable attenuator which concerns on the 1st Embodiment of this invention. It is a side view which shows a partially broken optical receiver with a built-in variable attenuator according to a second embodiment of the present invention. It is a figure which shows the characteristic of the code error rate of the optical receiver with a built-in variable attenuator which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

10, 20 Condensing lens 12, 22 Light receiving element 14, 24 VOA element 30 Signal light 32 Light receiving element 34 Light receiving surface 100, 200 Receiver 102, 202 VOA
104, 204 Condensing lens 106, 206 Light receiving element 108, 208 Electrical circuit component 110, 210 MSA package 112 Lead 120, 220 Optical fiber 130, 230 Housing 140, 240 Housing 150 Optical connector 160 Laser module 170 Ammeter

Claims (10)

An optical receiver with a built-in variable attenuator,
A condensing lens that condenses incident light from the optical fiber;
A light receiving element for receiving incident light from the condenser lens,
The condenser lens is arranged to form a converging optical system;
The variable attenuator is configured to adjust an attenuation amount of light received by the light receiving element by changing an optical path of the incident light. The optical receiver according to claim 1,
An optical receiver, further comprising an optical aperture between the condenser lens and the light receiving element. The optical receiver according to claim 1, wherein
The variable attenuator is located on the incident side of the condenser lens. The optical receiver according to any one of claims 1 to 3,
The optical receiver according to claim 1, wherein the variable attenuator is located on an exit side of the condenser lens. The optical receiver according to claim 1,
The variable attenuator is composed of a magneto-optical element. The optical receiver according to claim 1,
The variable attenuator is composed of a transmissive MEMS element. The optical receiver according to any one of claims 1 to 6,
The optical receiver is an avalanche photodiode. The optical receiver according to any one of claims 1 to 7,
The optical receiver, wherein the condensing lens and the light receiving element are configured so that an imaging magnification is in a range of 1 to 5. The optical receiver according to any one of claims 1 to 8,
An optical receiver, further comprising temperature adjusting means. The optical receiver according to claim 1,
An optical receiver housed in an MSA package.

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