JPH04103021U - optical receiver circuit - Google Patents

Abstract

(57) [Summary] [Structure] Optical-to-electrical conversion element 1 that converts an optical input signal into an electrical signal, and amplifiers 2, 3, and 4 that equalize and amplify the electrical signal.
, a gain control circuit 5 that controls the multiplication factor of the opto-electric conversion element and the gain of the amplifier, and a signal that divides the output signal of the amplifier into a signal for identification and reproduction and a signal for timing extraction. In an optical receiving circuit including a distributor 6, a timing extraction circuit 7 for extracting a clock signal, and an identification/regeneration circuit 8 for identification/regeneration based on the clock signal, the signal distributor 6 is configured to provide input to the identification/regeneration circuit 8. It is characterized by a distributed constant line type directional coupler having a transfer characteristic that distributes signals substantially without loss and without waveform deterioration, and generates a differential signal of the amplifier output signal and distributes it to the electrical timing extraction circuit 7. shall be. [Effect] The amplified output signal can be divided into two parts, one for identification and reproduction and one for clock extraction, in the gigabit region without waveform deterioration, and the signal distributor can have both distribution and differentiation functions.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention relates to optical receiver circuits, especially for large-capacity optical communications exceeding the gigabit range. It relates to optical receiving circuits used in communication systems.

0002

[Conventional technology]

In conventional optical receiving circuits, as shown in Figure 2, there is an adapter that converts an optical input signal into an electrical signal. Balanche photodiode (hereinafter referred to as APD) 1, amplifies the electrical signal Optical reception is performed by an amplifier consisting of a preamplifier 2, a variable gain amplifier 3, and a main amplifier 4. The signal is converted into an electrical signal, equalized and amplified, and the gain is controlled according to the output level of the main amplifier 4. The control circuit 5 controls the multiplication factor M of the ADP 1 and the gain of the variable gain amplifier 3. The output level of the main amplifier 4 is made constant against changes in the reception level. On the other hand, the main amplifier The output signal of 4 is a signal component composed of an emitter follower or a resistor divider, etc. The clock is divided into two by the distributor 10, and one is clocked by the differentiating circuit 11 and the clock extracting circuit 7. The lock signal is extracted, and the identification and regeneration circuit 8 outputs the other signal distributor 10. A signal is identified and reproduced at the timing of a clock signal.

0003

[Problem that the idea aims to solve]

In this conventional optical receiving circuit, when dividing the output signal of the main amplifier circuit 4 into two, the emitter Emitter follower or resistor divider signal divider 10 is used. It is difficult to realize high-speed operation in the gigabit region and distribute without waveform deterioration. There is also the problem that the resistance divider has a large distribution loss.

0004

[Means to solve the problem]

The circuit of the present invention includes an optical-to-electrical conversion element that converts an optical input signal into an electrical signal, and the electrical signal. an amplifier that equalizes and amplifies the optical signal, a multiplication factor of the optical-to-electrical conversion element, and the amplification a gain control circuit for controlling the gain of the amplifier; and a gain control circuit for identifying and reproducing the output signal of the amplifier. A signal divider that divides the signal into two, a signal and a signal for timing extraction, and a clock signal A timing extraction circuit that extracts the clock signal, and an identification reproduction circuit that performs identification reproduction based on the clock signal. In an optical receiving circuit having a circuit, The signal distributor reduces the waveform of the input signal to the identification and regeneration circuit with substantially no loss. The electrical timing extraction circuit generates a differential signal of the amplifier output signal. It is characterized by a distributed constant line type directional coupler having a transfer characteristic that distributes the distribution to the Ru.

[0005]

【Example】

Next, the present invention will be explained with reference to the drawings. Figure 1 shows a block diagram of one embodiment of the present invention. This is a diagram.

The electrical signal converted by the APD 1 is equalized and amplified by a preamplifier 2 , a variable gain amplifier 3 , and a main amplifier 4 , and the equalized output signal is input to an input port PORT 1 of a coupler 6 . The coupler 6 is a distributed constant line type directional coupler, and the transfer characteristics from the input port PORT1 of the coupler 6 to the output ports PORT2 and PORT3 when the output port PORT4 is terminated with a terminator 9 having a characteristic impedance Z ₀ are as follows. As shown in FIG. The equalized output signal input from the input port PORT1 becomes a differential signal at the output port PORT2, and is distributed as a lossless equivalent signal at the output port PORT3.

[0007] The differential signal obtained at the output port PORT2 of the coupler 6 is sent to the clock extraction circuit 7. The input clock signal is extracted, and this clock signal is input to the identification circuit 8. The equalized signal obtained at the output port PORT3 of the coupler 6 is identified and reproduced.

[0008]

[Effect of the idea]

As explained above, the present invention uses the equalized output signal for identification and reproduction and clock extraction. By using a distributed constant line type directional coupler as a signal splitter that divides the signal into two, This enables distribution without waveform deterioration in the gigabit domain, and also enables distribution functions and It has the effect of being able to have a differential function as well.

[Brief explanation of drawings]

[Figure 1] Block diagram of one embodiment of the present invention

[Figure 2] Block diagram of a conventional optical receiver circuit

FIG. 3 is a characteristic diagram illustrating the transfer characteristics of the coupler 6 in the embodiment of the present invention.

[Explanation of symbols]

1 Avalanche photodiode (APD) 2 Preamplifier 3 Variable gain amplifier 4 Main amplifier 5 Gain control circuit 6 Coupler 7 Clock extraction circuit 8 Identification and regeneration circuit 9 Terminal 10 Signal splitter 11 Differential circuit

Claims (1)

[Scope of utility model registration request] 1. An optical-electrical conversion element that converts an optical input signal into an electrical signal, an amplifier that equalizes and amplifies the electrical signal, and a gain that controls the multiplication factor of the optical-electrical conversion element and the gain of the amplifier. a control circuit, a signal for identifying and reproducing the output signal of the amplifier, and a signal for timing extraction;
In the optical receiving circuit, the signal distributor includes a signal distributor for distributing a signal, a timing extraction circuit for extracting a clock signal, and an identification reproducing circuit for discriminating and reproducing based on the clock signal. An optical optical system characterized by having a distributed constant line type directional coupler having a transmission characteristic that distributes the signal substantially without loss and without waveform deterioration, generates a differential signal of the amplifier output signal, and distributes it to an electrical timing extraction circuit. receiving circuit.