Optical module for receiving optical signal from optical fiber

Details Optical module for receiving optical signal from optical fiber Optical module for receiving optical signal from optical fiber

1998-07-16

2001-12-25

Chan, Jason (Department: 2633)

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

C250S2140AG

Reexamination Certificate

active

06333804

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical receiver which converts an optical signal fed into a photodiode to an electric signal.
2. Related Background Art
FIG. 14
shows a basic configuration of a conventional optical receiver. An optical signal OS is converted into its corresponding electric signal by a photodiode
1
. Thus formed photocurrent is converted into a voltage signal by a preamplifier (transimpedance amplifier, current-voltage converter circuit)
3
comprising an amplifier
3
a
and a transimpedance
3
b
, and the resulting signal is transmitted to a data-identifying/reproducing and clock-extracting circuit
4
.
It is often necessary for the conventional optical receiver to monitor an average input light intensity. Though the average value of the photocurrent generated in the photodiode has to be detected therefor, no circuit for this purpose can be inserted in the anode of the photodiode
1
. This is because the preamplifier
3
is connected to the anode of the photodiode
1
and, consequently, another circuit element connected thereto would deteriorate waveforms of signals, in particular, in high-frequency bands used for optical signal transmission.
SUMMARY OF THE INVENTION
The optical receiver in accordance with the present invention comprises a photodiode for receiving an optical signal emitted from an optical fiber; a current mirror circuit having two parallel lines with respective currents flowing therethrough at levels in proportion to each other, one of the lines being connected to one end of the photodiode; and a transimpedance amplifier connected to the other end of the photodiode.
In this optical receiver, in the case where the photodiode is cathode-grounded, since the current mirror circuit is provided, the photocurrent flowing into the photodiode can be amplified by the transimpedance amplifier and observed as a current flowing out of the photodiode by way of the other line. In the case where the photodiode is anode-grounded, since the current mirror circuit is provided, the photocurrent flowing out of the photodiode can be amplified by the transimpedance amplifier and observed as a current flowing into the photodiode by way of the other line.
Preferably, the optical receiver in accordance with the present invention further comprises a resin material for molding the transimpedance amplifier or current mirror circuit.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.


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