Optical signal receiving circuit and method for receiving optical signal

• US 6,396,614 B1
• Filed: 10/26/1998
• Issued: 05/28/2002
• Est. Priority Date: 10/24/1997
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Yoshizawa, Nobukazu
• Primary Examiner(s): Chan, Jason
• Assistant Examiner(s): Leung, Christina Y
• Application Number:
  US09/178,812
• Time in Patent Office: 1,310 Days
• Field of Search: 359/189,194,195 250/214 A,214 AG,214 R
• US Class Current: 398/202
• CPC Class Codes: H04B 10/6911 Photodiode bias control, e.g. for compensating temperature variations
• CPC Class Codes: H04B 10/6931 Automatic gain control of the preamplifier

Abstract

It is an object of the invention to provide an optical signal receiving circuit, which secures a dynamic range of a pre-amplifier used therein and can be simply designed without paying special attention to a gain-phase characteristic of a feed back circuit. A resistor is connected in series with a photodiode, and a signal voltage proportional to an input optical signal level is detected by a peak-detecting circuit, an output voltage of which is supplied to a gate of a FET connected in parallel with a fixed feed back resistor of a current feed back amplifier. The feed back resistance is controlled by internal conductance of the FET, which is changed by the gate voltage.

Claims

1. An optical signal receiving circuit, comprising:

a photodiode for converting and input optical signal into a current signal,

a current feed back amplifier for converting said current signal supplied from an anode of said photodiode into a voltage signal,

wherein input and output terminals of said current feed back amplifier are connected by a first resistor,

a second resistor inserted between a cathode of said photodiode and a terminal of a power supply for a reverse bias voltage,

wherein said reverse bias voltage of said cathode of said photodiode is supplied through said second resistor,

a peak-detecting circuit for detecting an amplitude of a receiving signal voltage generated by said current signal between both ends of said second resistor, and

an adjusting circuit for controlling a feed back current of said current feed back amplifier based on an output voltage of said peak-detecting circuit.

2. An optical signal receiving circuit according to claim 1, wherein:

said adjusting circuit is constituted of a FET,

wherein source and drain electrodes of said FET are respectively connected with input and output terminals of said current feed back amplifier, and a gate electrode of said FET is connected with an output terminal of said peak-detecting circuit.

3. An optical signal receiving circuit according to claim 2, wherein:

said FET decreases a conductance between said source and drain electrodes of said FET to decrease said feed back current of said current feed back amplifier in case that said output voltage of said peak detecting circuit increases, and increases said conductance between said source and drain electrodes of said FET to increase said feed back current of said current feed back amplifier in case that said output voltage of said peak detecting circuit decreases.

4. An optical signal receiving circuit according to claim 2, wherein:

said peak-detecting circuit is an amplifier of a liner characteristic so that said current feed back amplifier is not saturated.