JP4058646B2 - Optical signal processing device - Google Patents

Description

  The present invention relates to an optical signal processing device capable of high-speed operation.

  Conventionally, an optical repeater has three functions of equalization amplification (Reshaping), clock regeneration (Retiming), and identification regeneration (Regeneration). For example, it is shown in FIG. Such an optical repeater, even if waveform distortion or noise occurs in the optical data signal due to transmission, once regenerates it into an electrical digital signal, converts it back to an optical signal, and transmits it again. The resulting signal quality degradation is eliminated.

  Since such an optical repeater has a large scale, an apparatus as shown in FIG. Such an apparatus will be described with reference to FIG.

  In FIG. 13, a photodiode 1 receives input light and converts it into an electrical signal. The amplifier 2 receives an electric signal and amplifies it. The EA modulator (electroabsorption optical modulator) 3 changes the transmittance according to the electric signal from the amplifier 2 and modulates the light to output it.

  The operation of such an apparatus will be described below. The photodiode 1 receives an optical signal, converts it into an electrical signal, and outputs it to the amplifier 2. The amplifier 2 amplifies and outputs it to the EA modulator 3. The EA modulator 3 modulates light with the signal from the amplifier 2 and outputs an optical signal.

JP 2000-59313 A

  Such an apparatus cannot perform waveform shaping when the optical signal is dull. Thus, when performing waveform shaping, it is conceivable to provide the amplifier 2 with a waveform shaping function.

  However, in recent years, with the increase in the speed of optical signals, an operation of 100 GHz or more has been required, but there is a problem that the amplifier 2 cannot operate at a high speed.

  Therefore, an object of the present invention is to realize an optical signal processing device capable of high-speed operation.

The invention described in claim 1
At least two photodiodes having a cathode connected to a constant voltage and converting an optical signal into an electrical signal;
A resistor connecting one end to at least one anode of these photodiodes and connecting the other end to a constant voltage;
A resonant tunneling diode connected to one end of the resistor, the photodiode is provided at least in parallel or in series, and a logical sum or logical product is performed by input of light to the photodiode, and the load characteristic of the resistor It is an optical logic circuit that obtains a waveform-shaped digital signal by switching the resonant tunneling diode by switching the straight line and outputting it as an optical signal.
According to a second aspect of the invention, an invention of claim 1,
It has an optical modulator that is connected to one end of the resonant tunneling diode, changes its transmittance, and modulates and outputs light.
Invention of Claim 3 is invention of Claim 1 or 2, Comprising:
An electrical signal is obtained from one end of the resonant tunneling diode.
The invention according to claim 4
At least two photodiodes for converting optical signals into electrical signals;
A first resistor connecting one end to at least one anode of the photodiodes and connecting the other end to a first constant voltage;
A resonant tunneling diode connecting one end to one end of this resistor;
One end of the resonant tunneling diode is connected to the other end of the resonant tunneling diode, and a second resistor is connected to the other end of the resonant tunneling diode. The photodiode is provided at least in parallel or in series to transmit light to the photodiode. A logical sum or a logical product is performed according to the input, the load characteristic straight line of the first resistor is changed, and the resonant tunneling diode performs a switching operation to obtain a digital signal having a waveform shape, which is output as an optical signal. It is an optical logic circuit.
Invention of Claim 5 is invention of Claim 4 , Comprising:
It has an optical modulator that is connected to the other end of the resonant tunneling diode, changes the transmittance, and modulates and outputs the light.
Invention of Claim 6 is invention of Claim 4 or 5, Comprising:
An electrical signal is obtained from the other end of the resonant tunneling diode.

  According to the present invention, the optical signal is converted into an electrical signal by the photodiode, and the resonant tunnel diode performs a switching operation by the electrical signal, and a digital signal can be obtained along with the switching operation. There is an effect that it is small and can operate at high speed.

  Further, since the optical modulator changes the transmittance and modulates light in accordance with the switching operation of the resonant tunneling diode, an optical repeater having a small circuit scale and operating at high speed can be configured.

  In addition, since the logic can be obtained by the photodiode, the logic operation can be performed at high speed with a simple configuration.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a first embodiment of the present invention. In FIG. 1, a photodiode 4 converts an optical signal (digital signal) into an electrical signal. The resonant tunneling diode 5 is a negative resistance switching element in which a quantum well structure is formed and a resonant tunneling phenomenon of electrons is caused by using the quantum well. Since the resonant tunneling diode 5 has a quantum mechanical resonance effect, it can perform a switching operation for a high-speed electric signal of 100 Gb or more. The resonant tunneling diode 5 receives the electrical signal from the photodiode 4 and performs a switching operation. The EA modulator (electroabsorption optical modulator) 6 modulates and outputs light by changing the transmittance by the switching operation of the resonant tunneling diode 5.

  Next, a specific configuration will be described with reference to FIG. The photodiode 41 receives an optical signal and connects the cathode to the voltage V1. The resistor R has one end connected to the voltage V2 and the other end connected to the anode of the photodiode 41. The resonant tunnel diode 51 has one end connected to the other end of the resistor R and the other end grounded. Here, the connection point between the other end of the resistor R and the resonant tunneling diode 51 is assumed to be “X”. The EA modulator 61 connects the cathode to one end of the resonant tunneling diode 51, grounds the anode, and changes the transmittance. For example, the EA modulator 61 modulates and outputs constant light from an optical fiber. The resonant tunnel diode 51 and the EA modulator 61 are grounded to the same potential, but may be configured to be connected to different potentials.

  The operation of such a device will be described below. FIG. 3 is a diagram for explaining the operation of the apparatus shown in FIGS. 1 and 2, in which the horizontal axis represents voltage and the vertical axis represents current. A load characteristic curve a is a load characteristic curve of the resonant tunneling diode 51, and load characteristic straight lines b1 to b3 are load characteristic straight lines of the resistor R.

  When no light is input to the photodiode 41, the photodiode 41 does not pass current. Accordingly, the voltage at the connection point X is determined by the intersection A between the load characteristic curve a of the resonant tunnel diode 51 and the load characteristic line b1 of the resistor R, and is “v1”. Due to the voltage “v1”, the EA modulator 6 has a high transmittance, so that light is output.

  When light is input to the photodiode 41, the photodiode 41 passes a current, and the load characteristic straight line of the resistor R becomes “b2”. As a result, the voltage at the connection point X is determined by the intersection B between the load characteristic curve a of the resonant tunnel diode 51 and the load characteristic line b2 of the resistor R, and becomes “v2 (> v1)”. With this voltage “v2”, the EA modulator 61 has a low transmittance, and no light is output.

  Then, a dull digital waveform light as shown in FIG. 4A is input to the photodiode 41 as the input light, and when the input light becomes stronger, the current from the photodiode 41 increases and the voltage at the connection point X is increased. Becomes “v3” and suddenly becomes the voltage “v2”. As the current from the photodiode 41 increases, the voltage also slightly increases from “v2”.

  The input light in FIG. 4A passes the peak and starts to weaken, the current from the photodiode 41 decreases, the voltage at the connection point X becomes “v4”, and suddenly becomes the voltage “v5”. As the current from the photodiode 41 decreases, the voltage also slightly decreases from “v5”.

  As a result, as shown in FIG. 4B, the voltage at the connection point X becomes a digital waveform. Then, the EA modulator 61 is controlled by this voltage, and the output light shown in FIG. 4C is output, so that the dull input light can be reproduced as a steep digital waveform light. In the apparatus shown in FIG. 2, an optical signal inverted with respect to the input optical signal is output.

  In this way, the optical signal is converted into an electrical signal by the photodiode 41, and the resonant tunnel diode 41 performs a switching operation by this electrical signal. With this switching operation, the EA modulator 61 changes the transmittance, Since the light is modulated, the circuit scale is small and it can operate at high speed.

  Next, a method for manufacturing the apparatus shown in FIG. 2 will be described with reference to FIGS. FIG. 5 is a view showing a laminated structure of compound semiconductors, and FIG. 6 is a view showing a structure of the compound semiconductor of the apparatus shown in FIG.

In FIG. 5, a P ⁺ -InP layer 101, a (u) -InGaP layer 102, an n ⁺ -InP layer 103, an n ⁺ -InGaAs layer 104, an n ⁻ -InGaAs layer 105, an AlAs (InAlAs) layer are formed on an InP substrate 100. 106, (i) -InGaAs layer 107, AlAs (InAlAs) layer ^108, n - -InGaAs layer ^109, n + -InGaAs layer ^110, n - -InGaAs layer 111, (n ^-) -InP layer 112 laminated in this order Is formed. A Zn diffusion region 113 is formed in part of the n ⁻ -InGaAs layer 111 and the (n ⁻ ) —InP layer 112.

Then, etching is performed to form the electrode 114, the insulating film 115, and the wiring 116, which are formed as shown in FIG. As a ^result, n + a photodiode 41 formed in the Zn diffusion region 113 from -InGaAs layer 110 ^to form a resonant tunneling diode 51 in ⁿ + -InGaAs layer 110 from n + -InGaAs layer ^104, P + -InP layer 101 The EA modulator 61 is formed by the n ⁺ -InGaAs layer 104.

  Thus, since it can be formed on the same semiconductor substrate, the photodiode 41, the resonant tunnel diode 51, and the EA modulator 61 can be configured in one chip.

(Second embodiment)
Next, a second embodiment will be described with reference to FIG. In FIG. 7, the photodiode 42 receives an optical signal and connects the cathode to the voltage V3. The resistor R1 has one end connected to the voltage V4 and the other end connected to the anode of the photodiode 42. The resonant tunnel diode 52 has one end connected to the other end of the resistor R1. The resistor R2 has one end connected to the other end of the resonant tunneling diode 52 and the other end connected to the voltage V5. The EA modulator 62 has a cathode connected to the anode of the photodiode 42, an anode connected to the voltage V6, and the transmittance changes, and modulates and outputs constant light. Here, the connection point between one end of the resistor R2 and the cathode of the EA modulator 62 is set to “Y” in the relationship of V3, V4> V5, V6.

  The operation of such a device is almost the same as that of the device shown in FIG. 2, but the voltage change at the connection point Y is the reverse of the connection point X. Therefore, the EA modulator 62 can output an optical signal that is not inverted with respect to the input optical signal.

(Third embodiment)
Next, as an application, an example in which an optical signal processing device is used in an optical logic circuit will be described. FIG. 8 is a block diagram showing a third embodiment of the present invention, showing an inverting AND circuit. Here, the same components as those in FIG.

  In FIG. 8, photodiodes 411 and 412 are provided in place of the photodiode 41, are connected in series, and input different optical signals. That is, the photodiode 411 connects the cathode to the voltage V1. The photodiode 412 has a cathode connected to the anode of the photodiode 411 and an anode connected to the other end of the resistor R.

  The operation of such an apparatus will be described. When both the photodiodes 411 and 412 are not receiving light, the photodiodes 411 and 412 do not pass current. When light is input to either one of the photodiodes 411 and 412, the photodiodes 411 and 412 do not flow current because the photodiodes 411 and 412 that are not input light do not flow current. When light is input to both the photodiodes 411 and 412, the photodiodes 411 and 412 pass current. Other operations are the same as those of the apparatus shown in FIG.

  That is, the logical product of the optical signals input to the photodiodes 411 and 412 is obtained, and an inverted optical signal is output from the EA modulator 61.

(Fourth embodiment)
Next, a fourth embodiment of the inverting OR circuit will be described with reference to FIG. Here, the same components as those in FIG.

  In FIG. 9, photodiodes 413 and 414 are provided instead of the photodiode 41, are connected in parallel, and input different optical signals. That is, the photodiode 413 has a cathode connected to the voltage V1 and an anode connected to the other end of the resistor R. The photodiode 414 has a cathode connected to the voltage V1 and a cathode connected to the other end of the resistor R.

  The operation of such an apparatus will be described. When both the photodiodes 413 and 414 receive no light, the photodiodes 413 and 414 do not pass current. When light is input to at least one of the photodiodes 413 and 414, one of the photodiodes 413 and 414 passes a current. Other operations are the same as those of the apparatus shown in FIG.

  That is, the logical sum of the optical signals input to the photodiodes 413 and 414 is taken, and an inverted optical signal is output from the EA modulator 61.

(Fifth embodiment)
Next, an optical logic circuit combining the third and fourth embodiments will be described with reference to FIG. Here, the same components as those in FIG.

  In FIG. 10, photodiodes 415 to 417 are provided in place of the photodiode 41, and input different optical signals. The photodiode 415 has a cathode connected to the voltage V1 and an anode connected to the other end of the resistor R. The photodiode 415 and the photodiodes 416 and 417 are connected in parallel, and the photodiodes 416 and 417 are connected in series. The photodiode 416 connects the cathode to the voltage V1. The photodiode 417 has a cathode connected to the anode of the photodiode 416 and a cathode connected to the other end of the resistor R.

  The operation of such a device is substantially the same as the operation of the device shown in FIGS. 8 and 9, and the logical product of the optical signals input to the photodiodes 416 and 417 is taken, and this logical product and the photodiode 415 are input. ORed with the optical signal. Then, an inverted optical signal is output from the EA modulator 61.

(Sixth embodiment)
Next, another embodiment of the AND circuit will be described with reference to FIG. Here, the same components as those in FIG.

  In FIG. 11, photodiodes 421 and 422 are provided in place of the photodiode 42, are connected in series, and input different optical signals. That is, the photodiode 421 connects the cathode to the voltage V3. The photodiode 422 has a cathode connected to the anode of the photodiode 421 and a cathode connected to the other end of the resistor R1.

  The operation of such an apparatus will be described. When both the photodiodes 421 and 422 are not receiving light, the photodiodes 421 and 422 do not pass current. When light is input to either one of the photodiodes 421 and 422, the photodiodes 421 and 422 to which no light is input do not flow current, so the photodiodes 421 and 422 do not flow current. When light is input to both the photodiodes 421 and 422, the photodiodes 421 and 422 pass current. Since other operations are the same as those of the apparatus shown in FIG.

  That is, the logical product of the optical signals input to the photodiodes 421 and 422 is obtained, and the optical signal is output from the EA modulator 62.

(Seventh embodiment)
Another embodiment of the OR circuit will be described with reference to FIG. Here, the same components as those in FIG.

  In FIG. 12, photodiodes 423 and 424 are provided in place of the photodiode 42, are connected in parallel, and input different optical signals. That is, the photodiode 423 has a cathode connected to the voltage V3 and an anode connected to the other end of the resistor R1. The photodiode 424 has a cathode connected to the voltage V3 and an anode connected to the other end of the resistor R1.

  The operation of such an apparatus will be described. When both the photodiodes 423 and 424 are not receiving light, the photodiodes 423 and 424 do not pass current. When light is input to at least one of the photodiodes 423 and 424, a current flows when the light from the photodiodes 423 and 424 is input. Other operations are the same as those of the apparatus shown in FIG.

  That is, the logical sum of the optical signals input to the photodiodes 423 and 424 is taken, and the optical signal is output from the EA modulator 62.

  As described above, since the logic can be obtained by the photodiodes 411 to 417 and 421 to 424, a logical operation can be performed at high speed with a simple configuration.

  Note that the present invention is not limited to this, and the configuration in which the switching operation of the resonant tunneling diode 5 is output as light by the EA modulator 6 is shown. However, the switching operation of the resonant tunneling diode 5 is extracted by an electrical signal. It may be configured. For example, a signal is extracted from the connection point X shown in FIG. 2 or the connection point Y shown in FIG.

  Further, although the voltages V1 and V2 are shown as different voltages, they may be the same voltage value. Similarly, the voltages V3 and V4 may have the same voltage value. The voltages V5 and V6 may be the same voltage value.

  Although the logic circuit is shown in FIGS. 8 to 12, the logic circuit is not limited to this logic circuit, and the logic circuit can be configured by various combinations of photodiodes.

It is the block diagram which showed the 1st Example of this invention. It is the figure which showed the specific structure of the apparatus shown in FIG. It is a figure explaining operation | movement of the apparatus shown in FIG. It is a figure explaining operation | movement of the apparatus shown in FIG. It is the figure which showed the semiconductor laminated structure. It is the figure which showed the structure of the semiconductor of the apparatus shown in FIG. It is the block diagram which showed the 2nd Example of this invention. It is the block diagram which showed the 3rd Example of this invention. It is the block diagram which showed the 4th Example of this invention. It is the block diagram which showed the 5th Example of this invention. It is the block diagram which showed the 6th Example of this invention. It is the block diagram which showed the 7th Example of this invention. It is the figure which showed the structure of the conventional optical repeater.

Explanation of symbols

4, 41, 42, 411-417, 421-424 Photodiode 5, 51, 52 Resonant tunnel diode 6, 61, 62 EA modulator R, R1, R2 Resistor 100 InP substrate

Claims (6)

At least two photodiodes having a cathode connected to a constant voltage and converting an optical signal into an electrical signal;
A resistor connecting one end to at least one anode of these photodiodes and connecting the other end to a constant voltage;
A resonant tunneling diode connected to one end of the resistor, the photodiode is provided at least in parallel or in series, and a logical sum or logical product is performed by input of light to the photodiode, and the load characteristic of the resistor An optical signal processing device, which is an optical logic circuit that obtains a waveform-shaped digital signal by switching a resonant tunneling diode by switching a straight line, and outputs the digital signal as an optical signal. Resonant tunneling diode connected to one end of the transmission rate is changed, the optical signal processing apparatus according to claim 1, characterized in that it comprises a light modulator and outputting the modulated light. 3. The optical signal processing apparatus according to claim 1, wherein an electrical signal is obtained from one end of the resonant tunneling diode. At least two photodiodes for converting optical signals into electrical signals;
A first resistor connecting one end to at least one anode of the photodiodes and connecting the other end to a first constant voltage;
A resonant tunneling diode connecting one end to one end of this resistor;
One end of the resonant tunneling diode is connected to the other end of the resonant tunneling diode, and a second resistor is connected to the other end of the resonant tunneling diode. The photodiode is provided at least in parallel or in series to transmit light to the photodiode. A logical sum or a logical product is performed according to the input, the load characteristic straight line of the first resistor is changed, and the resonant tunneling diode performs a switching operation to obtain a digital signal having a waveform shape, which is output as an optical signal. An optical signal processing device characterized by being an optical logic circuit. 5. The optical signal processing apparatus according to claim 4, further comprising a modulator connected to the other end of the resonant tunneling diode, the transmittance changing, and modulating and outputting the light. 6. The optical signal processing apparatus according to claim 4 , wherein an electric signal is obtained from the other end of the resonant tunneling diode.

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