# US 5,706,118 A · Optical transmission method and optical transmission apparatus

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- Number: US 5,706,118 A
- Document ID: US5706118A
- Status: Granted
- Kind: A
- Application number: 08/627,344
- Filed: 1996-04-01
- Granted: 1998-01-06
- Earliest claimed: 1995-03-31
- Assignees: NEC Corporation
- Inventors: Isamu Takano
- Web page: https://patentgrep.com/patent/US5706118A

## CPC

- H04B 10/69: Electrical arrangements in the receiver
- H04B: TRANSMISSION

## Abstract

The invention provides a very high speed optical transmission apparatus which is tough against a variation in mark rate using an equalizing amplification circuit of a narrow-band frequency characteristic. The optical transmission apparatus includes an equalizing amplification circuit including a photoelectric conversion circuit for receiving a non-return-to-zero code as a reception signal, a peak value detection circuit, a dc amplifier, a timing extraction circuit, a dc regeneration circuit and an identification circuit. The equalizing amplification circuit includes a differentiating circuit for producing a differentiation equalization waveform of a reception signal of a non-return-to-zero code. The dc regeneration circuit includes a logic circuit for outputting logically positive and negative signals of an output signal of the equalizing amplification circuit, and a set-reset flip-flop circuit for receiving the logically positive signal of the output of the logic circuit as a set signal and receiving the logically negative signal of the output of the logic circuit as a reset signal. A full-wave rectification circuit is provided at an input terminal of the timing extraction circuit.

## Claims

### Claim 1

An optical transmission method for an optical transmission apparatus which includes an equalizing amplification section including a photoelectric conversion circuit for receiving a non-return-to-zero code as a reception signal, a timing extraction circuit, a dc regeneration circuit and an identification regeneration section, the optical transmission method comprising the steps of:
converting the reception signal of the non-return-to-zero code into a differentiation equalization code by said equalizing amplification section;
dc regenerating the reception signal of the non-return-to-zero signal using the differentiation equalization code by said dc regeneration circuit; and
extracting a timing signal using the differentiation equalization signal by said timing extraction section.

### Claim 2

An optical transmission apparatus, comprising:
an equalizing amplification circuit including a front end amplifier for amplifying a transmission signal obtained by photoelectric conversion, a differentiation circuit for producing a differentiation equalization signal from an output signal of said front end amplifier, and a variable gain amplifier and a post amplifier for amplifying an output signal of said differentiation circuit;
a peak value detection circuit for detecting a peak value of said equalizing amplification circuit and outputting a dc voltage corresponding to the peak value;
a dc amplifier for differentially amplifying the de voltage from said peak value detection circuit to control a gain of said variable gain amplifier;
a dc regeneration circuit including a logic circuit for outputting a logically positive signal and a logically negative signal of the output signal of said equalizing amplification circuit and a set-reset tip-flop circuit for receiving the logically positive signal of said logic circuit as a set signal and receiving the logically negative signal of said logic circuit as a reset signal;
a timing extraction circuit including a full-wave rectification circuit for full-wave rectifying the output signal of said equalizing amplification circuit, a timing extraction filter for extracting a timing signal from an output of said full-wave rectification circuit, and a narrow-band amplifier and a limiter amplifier for amplifying the timing signal; and
an identification circuit for waveform shaping an output signal of said dc regeneration circuit using the timing signal from said timing extraction circuit.