JP2513123B2 - Optical receiver - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiver used for optical communication, and more particularly to an optical receiver having improved response characteristics when a power source starts up.

[0002]

2. Description of the Related Art An optical receiver receives an optical signal by a light receiving element and amplifies it by a built-in amplifier to a required level (for example, Japanese Patent Laid-Open No. 3-128509, 3-2.
0522 publication).

FIG. 4 shows an example of the configuration of such a conventional optical receiver. The light receiving element 11 has its cathode side connected to a predetermined power source V _CC and its anode side connected to the input side of the amplifier 12. The output side of the amplifier 12 is connected to one input terminal of the comparator 13, and the predetermined reference voltage output from the reference voltage source 14 is connected to the other input terminal of the comparator 13.

In the optical receiver having the configuration shown in FIG. 4, when an optical signal is incident on the light receiving element 11, the photoelectrically converted signal is amplified by the amplifier 12 to a required level and input to the comparator 13. It Comparator 13
Has converted it into a binary digital signal (SIG) 15 by comparing it with a reference voltage. In a simple optical receiver having such a configuration, the reverse bias of the light receiving element 11 and the power sources of the amplifier 12, the comparator 13, and the reference voltage source 14 operate at a single 5 V as a common power source V _CC. It is generally done.

[0005]

In such a conventional optical receiver, the transient response at the time of the rise of the power supply is caused by the amplifier 12.
And the reference voltage source 14 independently. Therefore, in this transient response, there is a problem that it is difficult to guarantee the signal logic by the comparator 15 outside the allowable power supply voltage range.

Therefore, an object of the present invention is to provide an optical receiver capable of guaranteeing the logic at the time of binarizing a signal received by a light receiving element even in the transient response at the time of rising of a power supply.

[0007]

According to a first aspect of the present invention, a light receiving element for receiving an optical signal in an optical receiver, an amplifier for receiving and amplifying an output signal of the light receiving element, and a reference voltage are output. a reference voltage source, the power supply to set the comparator and transient response voltage is placed on the power supply of the amplifier by comparing the output signal of the output voltage and the amplifier of the reference voltage source for binarizing the output signal First end connected to
And one end is connected to the other end of this resistor and this other
Time constant composed of a first capacitor whose end is grounded
A constant generating circuit when the first number tau _1, the transient response voltage of the output power of the disposed power supply of the reference voltage source the reference voltage source to match the transient response voltage of the amplifier output signal
A second resistor connected to the power supply at one end and this second resistor
The second connector with one end connected to the other end and the other end grounded.
A second time constant generating circuit having a time constant τ ₂ composed of a capacitor and a power supply for the amplifier.
The time constant τ ₃ of the output voltage and the two time constants τ ₁ and τ described above.
₂ is

[Equation 2] It is characterized by being.

That is, according to the first aspect of the present invention, both the output of the amplifier input to the comparator and the reference signal have the same transient characteristic with respect to the common rise of the power supply, so that the output signal of the amplifier is set to 2 Since the reference signal for digitizing holds a relatively accurate level, it is possible to guarantee the signal logic even in the transient response at the rise of the power supply. According to the second and third aspects of the invention, the first and second time constant generating circuits are configured by resistors and capacitors each having one end connected to a common power source.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows the configuration of an optical receiver according to an embodiment of the present invention. In this embodiment, the light receiving element 11
Has a cathode connected to the power supply V _CC and an anode connected to the input terminal of the amplifier 12. This amplifier 12
Is supplied with the power supply V _CC via the first time constant circuit 21. The reference voltage source 14 is adapted to receive the supply of the power supply V _CC via the second time constant circuit 22. Each output is input to the input terminal of the comparator 13 and binarized digital signal (SIG) 2
3 is obtained.

FIG. 2 shows the circuit shown in FIG. 1 more specifically. The reference voltage source 14 is obtained by dividing the voltage between the power source V _CC and the ground GND by two resistors 31 and 32 connected in series. The first time constant circuit 21 is composed of a resistor 33 connecting between the power supply V _CC and the power supply input terminal of the amplifier 12, and a capacitor 34 connected between this power supply input terminal and the ground GND, and its time constant is τ.
_{Is 1} . The second time constant circuit 22 includes two resistors 31,
32 and a capacitor 37 connected between the connection point 36 and the ground GND. Its time constant is τ ₂ .

The time constant of the output voltage when the power of the amplifier 12 is turned on is τ ₃ . In this case, the other time constants τ ₁ and τ ₂ are set so that the following expression (1) holds.
The time constant τ ₃ is a unique value of the amplifier 12.

[0013]

[Equation 1]

FIG. 3 shows changes in the voltage of each part when the power source of the optical receiver of this embodiment rises. Here, the vertical axis represents the voltage, and the horizontal axis represents the passage of time from the rise of the power supply V _CC . When the power supply V _CC rises as shown in the figure, the potential of the connection point 36 connected to one output terminal of the comparator 13 by the second time constant circuit 22 rises curvilinearly as shown in FIG. The potential at the connection point 38 (FIG. 2) between the other input terminal of the comparator 13 and the amplifier 12 also shows a similar change due to the first time constant circuit 21. Therefore, if the light receiving element 11 receives an optical signal from a predetermined time t ₁ just after the rise of the power supply V _CC , the potential of the connection point 38 due to this is the potential of the connection point 36 (reference voltage) shown by the broken line. Voltage) as the center and swings in both the positive and negative directions.
It is possible to surely binarize the output signal of 1 to produce the digital signal 23.

[0015]

According to the present invention as described above, according to the present invention, co
With respect to the rise of the through power, Dara both name for both the amplifier output and the reference signal to be input to the comparator
Since it has the same transient characteristics that show a kana curve change ,
The reference signal for binarizing the output signal of the amplifier is relatively
Since a relatively accurate level is maintained from the initial stage, there is an effect that the allowable power supply voltage range in which the output signal logic of the comparator is guaranteed is greatly expanded as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of an optical receiver according to an embodiment of the present invention.

2 is a circuit diagram showing a specific circuit configuration of the optical receiver shown in FIG.

FIG. 3 is a waveform diagram showing a change in voltage input to the two input terminals of the comparator when the power supply V _CC rises in the optical receiver of the present embodiment.

FIG. 4 is a block diagram showing a configuration of a conventional optical receiver.

[Explanation of symbols]

11 light receiving element 12 amplifier 13 comparator 14 reference voltage source 21 first time constant circuit 22 second time constant circuit 23 digital signal V _CC power supply

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04B 10/14 10/18 10/26

Claims (1)

(57) [Claims] 1. A light receiving element for receiving an optical signal, an amplifier for inputting and amplifying an output signal of the light receiving element, a reference voltage source for outputting a reference voltage, an output voltage of the reference voltage source and the amplifier. A comparator for comparing the output signal with the output signal and binarizing the output signal; a first resistor arranged at a power supply portion of the amplifier and having one end connected to a power source for setting a transient response voltage;
One end was connected to the other end of resistor 1 and the other end was grounded
A first time constant generating circuit having a time constant τ ₁ composed of a first capacitor, and a transient response voltage of an output power source of the reference voltage source, which is arranged in a power supply section of the reference voltage source, and outputs a transient response voltage of the amplifier to the output of the amplifier. Connect one end to the power supply to match the transient response voltage of the signal.
Connected to the other end of the second resistor and the other end of the second resistor.
And a second capacitor whose other end is grounded.
And a second time constant generation circuit constant tau ₂ when, before
Note: Time constant τ of output voltage at power-on of amplifier
₃ and the two time constants τ ₁ and τ ₂ are given by Optical receiver, characterized in that it.