JPH0779203A - Optical receiver - Google Patents

Abstract

PURPOSE:To provide a small highly integratable new optical receiver capable of enlarging an optical input dynamic range. CONSTITUTION:This optical receiver receives light beams emitted from an optical fiber 13 at a photodetector 18, converts them into voltage signals by using a resistor 19 and passes the voltage signals through a signal amplifier 20. An optical modulator 16 is provided between the optical fiber 13 and the photodetector 18, a part of the signals outputted from the amplifier 20 passes through an amplitude detection circuit 21 and is feedback-controlled by the control circuits (22, 23) of the optical modulator 16 and a part of a current outputted from the photodetector 18 passes through a photodetector current detection circuit 22 and is feedback-controlled by the control circuit 23 of the optical modulator. Further, the optical receivers are formed on the same substrate and an optoelectronic integrated circuit is constituted or the plural sets of the electronic integrated circuits are formed on the same substrate and a groove is formed between the adjacent optical receivers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiver for receiving an optical signal, and more particularly to a compact and high-performance optical receiver capable of expanding a range of receivable light intensity.

[0002]

2. Description of the Related Art FIG. 6 shows the structure of a general optical receiver.
The light beam emitted from the optical fiber 1 is focused on the light receiving element 3 using the lens 2. A current is generated in the light receiving element 3 according to the received light intensity. This current is converted into a voltage signal using the resistor 4, amplified by the signal amplifier 5 and output as an optical reception signal.

If the optical signal transmitted through the optical fiber is larger than the maximum received power of the optical receiver, the optical receiver becomes an excessive input and the amplifier is saturated, or the photocurrent rating of the light receiving element is exceeded, for example. You will not be able to receive signals. In such a case, an optical attenuator is used to attenuate the light intensity so that an optical signal can be received. However, in that case, the receiving sensitivity of the optical receiver deteriorates by the amount of attenuation of the optical intensity of the optical attenuator.

FIG. 5 shows the configuration of an optical receiver equipped with an optical attenuator capable of varying the amount of attenuation of light intensity. The light beam emitted from the optical fiber 6 is converted into a parallel light beam by the first lens 7, passes through the light attenuating element 8, and then the second lens 9
Thus, the parallel beam is focused on the light receiving element 10. The light attenuating element 8 is formed by depositing a metal film on an optical glass plate. The light intensity is changed by inserting the light attenuating element 8 between the lenses 7 and 9. In addition, the light intensity attenuation amount can be continuously changed by using the light attenuation element in which the thickness of the vapor deposition film is continuously changed. By using this optical attenuator and mechanically changing the position of insertion between the lenses 7 and 9, an optical receiver with a wide dynamic range is realized.

[0005]

However, in an optical receiver including an optical attenuator composed of a combination of individual parts such as a lens and an optical attenuator as shown in FIG. 5, the optical attenuator 8 is mechanically provided. Since it has a structure to be moved to, it is extremely difficult to reduce the size and weight of the optical attenuator itself. In particular, when automating the change of the light intensity attenuation amount, a driving motor and this driving power source are further required, and there is a drawback that the size becomes larger and larger.

Further, two lenses are required to collect light on the light receiving element 10, and the optical axes of the components such as the optical fiber 6, the lenses 7 and 9 and the light receiving element 10 are required to be aligned. However, it is difficult to reduce the cost because it takes a lot of time and effort to assemble the optical receiver and requires individual adjustment.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, to provide a novel optical receiver capable of expanding the optical input dynamic range, being small in size and highly integrated.

[0008]

An object of the present invention is to provide an optical receiver which receives a light beam emitted from an optical fiber by a light receiving element, converts it into a voltage signal by using a resistor, and amplifies the voltage signal by an amplifier. In, an optical modulator is provided between the optical fiber and the light receiving element, and a part of the signal output from the amplifier is fed back to the control circuit of the optical modulator through an amplitude detection circuit for feedback control. An optical receiver characterized by: the optical modulator, the light receiving element, the amplitude detection circuit,
And the control circuit of the optical modulator is formed on the same substrate, the optical receiver described above, characterized in that it constitutes an optoelectronic integrated circuit, a plurality of sets of the optoelectronic integrated circuit is formed on the same substrate,
A groove is formed between adjacent optoelectronic integrated circuits, wherein the optical receiver is configured by using an optical switch capable of continuously switching an optical path in place of the optical modulator. The optical receiver according to any one of the above, receiving the light beam emitted from the light beam with a light receiving element,
In an optical receiver that converts an electric signal using a resistance and amplifies the voltage signal by an amplifier, an optical modulator is provided between the optical fiber and the light receiving element, and one of the currents output from the light receiving element is provided. An optical receiver characterized by performing feedback control by sending a part to a control circuit of the optical modulator via a light receiving element current detection circuit, the optical modulator, the light receiving element, the light receiving element current detection circuit, and The control circuit of the optical modulator is further formed on the same substrate, and the optical receiver described above, characterized in that an optoelectronic integrated circuit is configured, a plurality of sets of the optoelectronic integrated circuit are formed on the same substrate,
A groove is formed between adjacent optoelectronic integrated circuits, wherein the optical receiver is configured by using an optical switch capable of continuously switching an optical path in place of the optical modulator. The optical receiver according to any one of items 1 to 3 above.

In the present invention, the material and substrate of the optical waveguide and the optical modulator are not limited to semiconductors, but may be glass, strong derivatives, organic polymer materials, etc., as long as light can be confined and transmitted in the waveguide.

The light non-reflective terminal portion formed at the end of the terminal not connected to the transmission line of the optical modulator has an optical waveguide having a structure for diffusing or absorbing the light distributed to the terminal, for example, a rough side surface of the core. It can be constituted by a waveguide, a mixture of bubbles, a waveguide with large radiation loss, or the like. In addition, it suffices to take antireflection measures such as cutting the end face to which the antireflection coating film is attached obliquely with respect to the optical waveguide.

[0011]

【Example】

(Embodiment 1) FIG. 1A shows an embodiment of the present invention. The optical fiber 13, the semiconductor substrate 14, and the optical modulator 16 formed on the semiconductor substrate 14 at the intersection of two optical waveguides of the optical waveguide 15 formed of a semiconductor material in a pattern intersecting at the center as shown in the figure, Optical non-reflective terminal 17, light receiving element 18, resistor 1 for converting the photocurrent of the light receiving element into a voltage signal
9, signal amplifier 20, amplitude detection circuit 21, error amplifier 2
2. An optical modulator drive circuit 23 that supplies a current to the optical modulator.

The light beam propagating through the optical fiber 13 enters the optical waveguide 15 and reaches the optical modulator 16 from the terminal a. The optical modulator 16 switches the light incident from the terminal a to the terminal b side or the terminal c side by the current supplied from the optical modulator driving circuit 23. The switching is realized by changing the refractive index at the intersecting portion of the two optical waveguides, that is, the center of the optical modulator 16 by the injection current. When no current is injected, the refractive index of the optical modulator 16 is the same as that of the optical waveguide 15. Therefore, all the light beams incident from the terminal a pass through the optical modulator 16 and propagate to the terminal c side. When a current is injected, the refractive index of the optical modulator 16 becomes lower than that of the optical waveguide 15. Then, the light beam coming from the terminal a side is reflected by the optical modulator 16 and proceeds to the terminal b side. Light modulator 16
3 shows the relationship between the injection current and the light reflectance. From this figure, it can be seen that the intensity of the light beam transmitted from the terminal a to the terminal c can be controlled by 0 to 100% by changing the injection current to the optical modulator 16.

The light beam emitted from the terminal c is received by the light receiving element 1.
It is incident on 8. The light receiving element 18 photoelectrically converts the optical signal, and the resistor 19 converts the optical signal into a voltage signal. This voltage signal is amplified by the signal amplifier 20 and output as a reception signal. On the other hand, the peak value of the received signal amplitude is detected using the amplitude detection circuit 21. The detection signal is sent to the error amplifier 22.
Is compared with the reference voltage and error-amplified, and the output current of the optical modulator drive circuit 23 is controlled by the output signal. As a result, regardless of the intensity of the light beam propagating through the optical fiber 13, light of a certain light intensity level or less is always input to the light receiving element.

That is, the feature of the present invention resides in that the amplitude detection circuit 21 is used to detect the amplitude of the optical reception signal to control the optical modulator 16. The output of the amplitude detection circuit 21 is used to control the optical modulator 16 by changing the output current of the optical modulator control circuit configured by the error amplifier 22 and the optical modulator drive circuit 23. Therefore, the present invention can significantly improve the maximum reception power characteristic as compared with the conventional optical receiver having no optical modulator.

(Embodiment 2) FIG. 2 shows another embodiment according to claim 5 of the present invention. Optical fiber 13, semiconductor substrate 1
4. An optical modulator 16 formed on the semiconductor substrate 14 at the intersection of two optical waveguides of an optical waveguide 15 formed of a semiconductor material in a pattern intersecting at the center as shown in the figure, and an optical non-reflective terminal portion 17. , A light non-reflection coating film 24, a lens 9, a light receiving element 18, a resistor 25, a capacitor 26, an error amplifier 22, a resistor 19 for converting a photocurrent into a voltage signal, and a signal amplifier 20. The surface of the lens 9 and the light receiving surface of the light receiving element 18 are coated with no light reflection.

The light beam propagating through the optical fiber 13 enters the optical waveguide 15 from the terminal a and reaches the optical modulator 16. The optical modulator 16 switches the light incident from the terminal a to the terminal b side or the terminal c side by the current supplied from the optical modulator driving circuit 23. The switching is realized by changing the refractive index at the intersecting portion of the two optical waveguides, that is, the center of the optical modulator 16 by the injection current. When no current is injected, the refractive index of the optical modulator 16 is the same as that of the optical waveguide 15. Therefore, all the light beams incident from the terminal a pass through the optical modulator 16 and propagate to the terminal c side. When a current is injected, the refractive index of the optical modulator 16 becomes lower than that of the optical waveguide 15. Then, the light beam coming from the terminal a side is reflected by the optical modulator 16 and proceeds to the terminal b side. The relationship between the injection current and the light reflectance of the optical modulator 16 is as shown in FIG. 3 as in the first embodiment. From this figure, terminal a to terminal c
It is understood that the intensity of the light beam transmitted to the optical modulator 16 can be controlled by 0 to 100% by changing the injection current to the optical modulator 16.

The light beam emitted from the terminal c is focused on the light receiving element 18 by the lens 9. The average value of the photocurrent generated by the incident light on the light receiving element 18 is detected using the resistor 25 and the capacitor 26. The detection signal is sent to the error amplifier 22.
The error is amplified with the output signal and the optical modulator drive circuit 2
3 output current is controlled. As a result, light having a certain light intensity level or more is always input to the light receiving element regardless of the intensity of the light beam propagating through the optical fiber 13. Therefore, the present invention, compared to conventional optical receivers without optical modulators,
It is possible to greatly improve the maximum reception current characteristic.

In this embodiment, the lens 9 can be omitted.

(Embodiment 3) Another modification shown in claims 2, 3 or 6, 7 of the present invention is shown in FIG. The optical fiber 27, the semiconductor substrate 28, and the optical receiver of the present invention formed on the semiconductor substrate 28 (the optical waveguide 29, the optical modulator 30, the light receiving element 31, and the received signal amplification circuit, the amplitude detection circuit,
A plurality of optical reception control circuits 32) including an error amplifier and an optical modulator driving circuit or including a light receiving element current detection circuit and an optical modulator control circuit are formed on the same substrate, and a groove 34 is formed between each set. Has been formed.

By the semiconductor process, the optical receiver of the present invention can be formed on the same substrate, and a plurality of optical receivers can be simultaneously formed.

Optical waveguides of adjacent optical receivers by integration,
When the distance between the optical modulator and the light receiving element becomes small, the light emitted from the light non-reflective terminal 33 leaks into the optical waveguide, the optical modulator, and the light receiving element portion of the adjacent optical receiver, and the adjacent optical receiver. Crosstalk between them may be exacerbated. To prevent such an influence, a groove 34 is formed between adjacent optical receivers to prevent crosstalk between the optical receivers. The groove is formed by etching or mechanical processing.

In the optical receiver of the present invention, the optical variable attenuator of the optical receiver is configured by using the optical modulator whose reflectance can be continuously changed. However, the optical intensity can be obtained by other types of optical modulators or optical switches. Can be applied if it can be changed continuously.

Instead of the resistor 19 and the signal amplifier 20 shown in FIG. 1, the transimpedance type amplifier shown in FIG. 1B can be applied.

[0024]

The optical receiver of the present invention can automatically keep the light intensity input to the light receiving element below a certain value. Therefore, in contrast to the conventional optical receiver that does not have a variable optical attenuator,
Since the maximum reception power is no longer limited, the dynamic range can be greatly expanded. In particular, the output light of a high-power LD or optical amplifier can be directly received. In addition, damage to the light receiving element and the received signal amplifier due to excessive input is prevented. The dynamic range of the light receiving element and the reception signal amplifier can be reduced, and as a result, the light receiving element and the reception signal amplifier having high sensitivity characteristics can be applied. Therefore, an optical receiver having higher sensitivity and a wider input dynamic range can be realized.

By forming the optical modulator on the substrate,
The optical receiver can be reduced in size, weight and integration. Further, since a plurality of optical modulators can be formed on the substrate at the same time, it is possible to minimize the increase in size and manufacturing cost with respect to the increase in the number of optical receivers. Therefore, it is particularly effective to apply the present invention as an optical receiver for optical parallel transmission such as an optical data bus.

Compared with the conventional optical receiver, the light receiving element and the optical fiber can be connected without using a lens, so that the number of parts can be reduced. Further, since it is not necessary to adjust the distance between the lens and the optical fiber, it is possible to save the labor at the time of assembling and improve the accuracy of optical axis alignment. The labor of adjusting the optical axis can be significantly reduced, and thus the manufacturing cost can be reduced. Since the optical fiber and the light receiving element can be connected to each other by using the optical waveguide without using a lens, deviation of the coupling due to temperature fluctuation and vibration does not occur. Therefore, it is possible to suppress the fluctuation of the light intensity attenuation amount and improve the reliability of the optical receiver.

By using a large-area substrate and utilizing the photolithography technique, a large number of optical receivers can be accurately manufactured at one time, and the cost can be reduced.

Since the optical multiplexer / demultiplexer using the optical waveguide, the optical branching device, and the like can be manufactured at the same time, a high-density and highly-functional optoelectronic integrated circuit can be configured with them.

[Brief description of drawings]

FIG. 1A is a circuit diagram of an embodiment of an optical receiver of the present invention, and FIG. 1B is a diagram showing a transimpedance type amplifier.

FIG. 2 is a circuit diagram of another embodiment of the optical receiver of the invention.

FIG. 3 shows operating characteristics of the optical modulator of the optical receiver of the present invention.

FIG. 4 is a schematic circuit diagram of a modified example of the optical receiver of the present invention.

FIG. 5 is a circuit diagram of an optical receiver having a conventional optical attenuator.

FIG. 6 is a circuit diagram of a conventional optical receiver.

[Explanation of symbols]

 1,6,13,27 Optical fiber 2,7,9 Lens 3,10,18,31 Light receiving element 4,11,19,25 Resistor 5,12,20 Signal amplifier 8 Optical attenuation element 14,28 Semiconductor substrate 15, 29 Optical Waveguide 16,30 Optical Modulator 17,33 Optical Non-Reflection Termination Unit 22 Error Amplifier 23 Optical Modulator Drive Circuit 24 Optical Anti-Reflection Coating Film 26 Capacitor 32 (Optical Reception Control Circuit) Electronic Circuit 34 Grooves a, b, c , D Optical input / output terminal of optical modulator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04B 10/04 10/06 G01J 1/44 Z 8117-2G H01L 31/02 9372-5K H04B 9 / 00 S

Claims (8)

[Claims] 1. An optical receiver in which a light beam emitted from an optical fiber is received by a light receiving element, converted into a voltage signal by using a resistor, and the voltage signal is amplified by an amplifier, the optical fiber and the light receiving element. An optical receiver, wherein an optical modulator is provided between the optical modulator and a part of the signal output from the amplifier is sent to a control circuit of the optical modulator via an amplitude detection circuit for feedback control. 2. The optoelectronic integrated circuit according to claim 1, wherein the optical modulator, the light receiving element, the amplitude detection circuit, and the control circuit of the optical modulator are formed on the same substrate to constitute an optoelectronic integrated circuit. Optical receiver. 3. The optical receiver according to claim 2, wherein a plurality of sets of the optoelectronic integrated circuits are formed on the same substrate, and a groove is formed between adjacent optoelectronic integrated circuits. 4. The optical receiver according to claim 1, wherein an optical switch capable of continuously switching an optical path is used instead of the optical modulator. 5. An optical receiver in which a light beam emitted from a light beam is received by a light receiving element, converted into a voltage signal by using a resistor, and the voltage signal is amplified by an amplifier, wherein the optical fiber and the light receiving element are provided. An optical receiver characterized in that an optical modulator is provided between the optical receiver and a part of the current output from the light receiving element is sent to a control circuit of the optical modulator through a light receiving element current detection circuit for feedback control. . 6. An optoelectronic integrated circuit is formed by forming the optical modulator, the light receiving element, the light receiving element current detection circuit, and the control circuit of the optical modulator on the same substrate. 5. The optical receiver according to item 5. 7. The optical receiver according to claim 6, wherein a plurality of sets of the optoelectronic integrated circuits are formed on the same substrate, and a groove is formed between adjacent optoelectronic integrated circuits. 8. The optical receiver according to claim 5, wherein an optical switch capable of continuously switching an optical path is used instead of the optical modulator.