JP5475850B1 - Charge / discharge MSM-PD circuit - Google Patents

Abstract

A charge / discharge type MSM-PD circuit capable of repeatedly generating electric pulses at high speed is provided.
An MSM-PD ₁ 110 is connected in parallel to an input resistor 120 to which a bias voltage (V _in ) is applied, a charging capacitor 130, and a variable current source 150, and a parallel resistor 140 is connected to the other end. . The variable current source 150 includes a gate terminal and a drain terminal connected to each other and the HEMT 151 operating in a saturation mode, and the MSM-PD ₂ 152 disposed between the source terminal of the HEMT 151 and the charging capacitor 130. The HEMT 151 has a charge voltage (V _charge ) applied to its gate terminal and drain terminal, and functions as a constant current source. The MSM-PD ₂ 152 functions as a valve that turns on and off the current output from the HEMT 151 at an accurate timing in accordance with the irradiated light trigger pulse.
[Selection] Figure 1

Description

  The present invention relates to a charge / discharge MSM-PD circuit controlled by an optical trigger pulse.

  In recent years, with the explosive increase in data communication represented by the Internet, there has been an increasing demand for high speed and large capacity optical communication. Furthermore, future optical communication networks will need to be flexible enough to handle various network services and expandable to handle the types of services and the number of users.

  In response to the above problems, communication using optical packets can realize a network with the highest bandwidth utilization efficiency, flexibility, and expandability with fine data granularity. In order to realize optical packet communication, several functions are required. First, it is necessary to generate an asynchronous burst optical packet which is an original signal.

  In this packet generation operation, the memory medium in which the original packet data is held is mainly a silicon-based random access memory (RAM), but the interface speed of the silicon RAM itself is limited per Gbps, It is difficult to output a packet signal directly from a memory medium.

  Therefore, to generate a packet signal, data is output from a memory medium as a plurality of low-speed parallel electric signals, and the parallel electric signals are converted by an electric clock signal generator and an electric parallel-serial converter using high-speed electronic circuit technology. Conversion to a high-speed serial electric signal is considered. Then, an optical packet signal is generated by the subsequent electro-optic conversion.

  However, when converting a plurality of low-speed signals to a high-speed signal in this way, it is necessary to sequentially multiply the low-speed electrical signal to a double speed (that is, several hundred MHz →... → 20 GHz → 40 GHz). Therefore, a considerable number of stages are required, and clock generation at each stage is necessary. Furthermore, there is a problem of phase shift of the input parallel signal for each stage.

  On the other hand, there is a standard of Serdes-Framer Interface (SFI) that performs phase control, but the electronic circuit technology for executing this control is very complicated, and the number of devices (Flip-Flop) increases. The power consumption of the entire device will increase. Furthermore, although this control method performs clock recovery for each parallel signal, it is not possible to extract the clock instantaneously for signals input in an asynchronous burst.

  As a method for solving these problems, an optical clock transistor array (OCTA) optoelectronic circuit has been developed to realize an electro-optic parallel-serial converter (see Non-Patent Document 1).

FIG. 3 is a schematic diagram showing the configuration of a conventional optical clock transistor array (OCTA). Incidentally, in FIG. 3, 301-1 through 301-N are MSM-PD (Metal-Semiconductor- Metal Photo Detector), (V M) is MSM-PD bias voltage, 302-1 through 302-N are input resistor, 303 −1 to 303-N are charging capacitors, 304-1 to 304-N are high electron mobility transistors (HEMT), (P) is a light pulse, (V _b ) is a bias voltage, and 305-1 to 305-N. Is a parallel resistance, (S _ON ) is an ON signal, (SP) is an input parallel electrical signal, and (SS) is an output serial electrical signal.

  As shown in FIG. 3, in the conventional OCTA, N optical trigger transistor circuits 300-1 to 300-N are attached in parallel to one transmission line 310, and each optical trigger transistor circuit 300- 1 to 300-N are mainly composed of HEMTs 304-1 to 304-N and MSM-PDs 301-1 to 301-N attached to the gate terminals of HEMTs 304-1 to 304-N.

The packet data is output as input parallel electrical signals (SP _{1 to} SP _N ) from the CMOS memory, and each is supplied to the drain terminals of the HEMTs 304-1 to 304-N. The gate terminals of the HEMTs 304-1 to 304-N are set to a normally-off state by applying a bias voltage (V _b ), and the input parallel electrical signals (SP _{1 to} SP _N ) flow into the transmission line 310. There is no such thing.

Next, when the MSM-PD 301-1 to 301 -N are irradiated with an optical trigger pulse (P _{1 to} P _N ), the electric pulse generated there rises until it exceeds the threshold value of the gate voltage, and the HEMTs 304-1 to 304 -N. Is turned on, so that the input parallel electrical signals (SP _{1 to} SP _N ) are output on the transmission line 310 while the electric pulse disappears (that is, while the HEMTs 304-1 to 304-N are ON). . At this time, when the input parallel electric signals (SP _{1 to} SP _N ) input are “1”, the electric pulse propagates on the transmission line 310, and when it is “0”, it is not output.

Accordingly, the N inputs output from the CMOS memory are sequentially applied to the N MSM-PDs 301-1 to 301 -N by sequentially irradiating the optical trigger pulses (P _{1 to} P _N ) with a constant time difference τ. It is converted into an output serial electric signal (SS) having the same data as the parallel electric signals (SP _{1 to} SP _N ).

The output serial electric signal (SS) thus output is converted into a serial optical signal by electro-optical conversion using an optical modulator or the like. Further, the irradiation of the optical trigger pulse (P _{1 to} P _N ) and the bit input of the input parallel electric signals (SP _{1 to} SP _N ) in each of the optical trigger transistor circuits 300-1 to 300-N are performed at a certain period (T = Nxτ), it is possible to generate a burst optical packet having an arbitrary length.

Ryohei Urata, 4 others, “An Optically Clocked Transistor Array FOR High-Speed Asynchronous Label Swapping: 40 Gb / s AND BEON O L J 26, NO. 6, March 15, 2008, p. 692-703

  However, in the conventional parallel-serial converter using the slow charge / fast discharge (MSM-PD) type, it takes time until it is recharged once discharged. There was a problem that it was not possible. For this reason, the application target of the conventional parallel-serial converter is limited to a short data signal, for example, a label signal of an optical packet.

  The present invention has been made in view of such problems, and an object thereof is to provide a charge / discharge type MSM-PD circuit capable of repeatedly generating electric pulses at high speed.

  In order to solve the above problems, the present invention is a charge / discharge MSM-PD circuit, which is charged with the bias voltage, the first MSM-PD to which a bias voltage is applied, and the first MSM. A capacitor connected to the PD so as to be able to be discharged, and a variable current source connected to the capacitor so as to be able to be charged, including a constant current source and a second MSM-PD for turning on and off the constant current source An optical trigger pulse for irradiating the first MSM-PD is emitted after the charge generated by the optical trigger pulse being applied to the second MSM-PD is eliminated. To do.

  According to a second aspect of the present invention, in the charge / discharge type MSM-PD circuit according to the first aspect, the constant current source is a HEMT operating in a saturation mode in which a gate terminal and a drain terminal are connected. And

  The invention according to claim 3 is an optical trigger transistor circuit, wherein the charge / discharge MSM-PD circuit according to claim 1 or 2 and an output terminal of the charge / discharge MSM-PD circuit are at a gate terminal. And a connected HEMT.

  The present invention makes it possible to repeatedly generate electrical pulses at high speed in a charge / discharge MSM-PD circuit. In addition, the present invention enables high-speed recharging in a phototrigger transistor circuit using a charge / discharge MSM-PD circuit, and enables high-speed repetitive operation of the phototrigger transistor circuit.

It is the schematic diagram which showed the structure of the charge / discharge type MSM-PD circuit which concerns on one Embodiment of this invention. The charging capacitor voltage in the charge / discharge type MSM-PD circuit of the present invention, the timing of irradiating MSM-PD ₁ and MSM-PD ₂ with a light trigger pulse, and the amount of charge in MSM-PD ₁ and MSM-PD ₂ are shown. FIG. It is the schematic diagram which showed the structure of the conventional optical clock type transistor array (OCTA).

  Hereinafter, embodiments of the present invention will be described in detail.

FIG. 1 shows a configuration of a charge / discharge MSM-PD circuit according to an embodiment of the present invention. The MSM-PD ₁ 110 is connected in parallel to the input resistor 120 to which the bias voltage (V _in ) is applied, the charging capacitor 130, and the variable current source 150, and the parallel resistor 140 is connected to the other end.

The variable current source 150 includes a gate terminal and a drain terminal connected to each other and the HEMT 151 operating in a saturation mode, and the MSM-PD ₂ 152 disposed between the source terminal of the HEMT 151 and the charging capacitor 130. The HEMT 151 has a charge voltage (V _charge ) applied to its gate terminal and drain terminal, and functions as a constant current source. The MSM-PD ₂ 152 functions as a valve that turns on and off the current output from the HEMT 151 at an accurate timing in accordance with the irradiated light trigger pulse.

The optical trigger pulses P ₁ and P ₂ applied to the MSM-PD ₁ 110 and the MSM-PD ₂ 152 are, as described below, the optical trigger pulse P ₁ for a predetermined time with respect to the optical trigger pulse P ₂ . Controlled to be delayed. Such light trigger pulse P ₁ is, for example, branches the optical trigger pulse P ₂ into two signals on PLC (planar lightwave circuit), one is output as the optical trigger pulse P _2, described in the other following It is obtained by outputting a light trigger pulse P ₁ through the delay line corresponding to the delay amount required for the operation to be. In addition, a combination of an optical fiber coupler (branch circuit) and an optical fiber (delay circuit) having a length corresponding to a required delay amount can be realized.

  Note that an optical trigger transistor circuit can be configured by connecting the output terminal of the charge / discharge MSM-PD circuit 100 to the gate terminal of the HEMT 200.

FIG. 2 shows the voltage of the charging capacitor in the charge / discharge type MSM-PD circuit of the present invention, the timing of irradiating the MSM-PD ₁ and MSM-PD ₂ with the optical trigger pulse, and the MSM-PD ₁ and MSM-PD ₂ Indicates the amount of charge.

First, the MSM-PD ₂ 152 is irradiated with the optical trigger pulse P ₂ , and photoexcited carriers, that is, charges composed of electrons and holes are generated in the MSM-PD ₂ 152. Then, current is applied from the MSM-PD ₂ 152 to the charging capacitor 130 until the charging capacitor 130 reaches the voltage (V _R ). Since this process does not depend on the resistance value of the input resistor 120, the charge capacitor 130 is charged more rapidly than in the conventional example.

When the voltage of the charging capacitor 130 reaches _{(V R),} the current output from the _MSM-PD 2 152 since the potential difference across the _MSM-PD 2 152 smaller stops (Fig. 2, (b)). On the other hand, the charging capacitor 130 is further charged by the current applied from the input resistor 120.

Charge in _MSM-PD 2 152 also while stopping the current from the _MSM-PD 2 152, continued to decrease by recombination of electrons and holes, the resistance of the _MSM-PD 2 152 is becomes larger (Fig. 2, (a)).

When the voltage of the charging capacitor 130 reaches (V _R + Δ), a leakage current is generated due to the charge in the MSM-PD ₂ 152 moving to the HEMT 151 side (FIG. 2, (c)). Since the leakage current is very small, the influence on the charging amount of the charging capacitor 130 is small, and the charge in the MSM-PD ₂ 152 disappears and becomes zero.

When the charge in the MSM-PD ₂ 152 is exhausted, the optical trigger pulse P ₁ is irradiated to the MSM-PD ₁ 110 (FIG. 2, (d)). Since there is no charge in MSM-PD ₂ 152, all charges in MSM-PD ₁ 110 flow to the desired parallel resistance 140 side. That is, MSM-PD ₂ 152 does not affect the output pulse of MSM-PD ₁ 110.

As described above, according to the present invention, the time required to reach the voltage (V _R ) of the charging capacitor 130 is greatly reduced, while the output pulse can be the same as the conventional one.

  The present invention provides a variable current source to the charge / discharge type MSM-PD circuit of the conventional photo-trigger type transistor circuit, thereby operating without changing the high-speed pulse response characteristic (discharge characteristic) of the photo-trigger type transistor circuit. Can be recharged at high speed.

100 charge / discharge MSM-PD circuit 110, 152 MSM-PD
120 Input Resistance 130 Charging Capacitor 140 Parallel Resistance 150 Variable Current Source 151 HEMT

Claims (3)

A first MSM-PD to which a bias voltage is applied;
A capacitor charged with the bias voltage and connected to the first MSM-PD for discharge;
A variable current source including a constant current source and a second MSM-PD for turning on and off the constant current source, and connected to be able to charge the capacitor;
And the first MSM-PD is irradiated with the light trigger pulse after the charge generated by the irradiation of the second MSM-PD with the light trigger pulse disappears. MSM-PD circuit.   2. The charge / discharge MSM-PD circuit according to claim 1, wherein the constant current source is a HEMT operating in a saturation mode in which a gate terminal and a drain terminal are connected. The charge / discharge MSM-PD circuit according to claim 1 or 2,
A photo-trigger type transistor circuit comprising: a HEMT having an output terminal of the charge / discharge MSM-PD circuit connected to a gate terminal.

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