Coherent light generators – Particular component circuitry – Optical pumping
Reexamination Certificate
1998-08-20
2001-03-13
Font, Frank G. (Department: 2881)
Coherent light generators
Particular component circuitry
Optical pumping
C359S199200
Reexamination Certificate
active
06201822
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an optical signal transmission apparatus, an optical signal propagation apparatus, and an optical signal transmission method, and more particularly, to an optical signal transmission apparatus, an optical signal propagation apparatus, and an optical signal transmission method that convert multiple electrical signals into optical signals, and batch-transmit these optical signals via optical fibers.
2. Description of Related Art
An example of a conventional optical signal transmission apparatus will be explained with reference to FIG.
1
. In
FIG. 1
, reference numeral
1
refers to a transmission side LSI composed of a CMOS, Bi-CMOS, bipolar, GaAs or the like which is a logic circuit for processing multiple electric signals separately. Reference numeral
11
refers to a laser driver for amplifying an output electric signal of the transmission side LSI
1
. Reference numeral
12
refers to a laser diode or a laser diode array, which generates an optical signal that corresponds to this output electric signal driven by the output electric signal that has been amplified by the laser driver
11
. Reference numeral
13
refers to an optical connector. Reference numeral
3
refers to an optical fiber or optical fiber tape. The laser diode
12
is optically coupled with the optical fiber
3
via the optical connector
13
. The optical signal generated by the laser diode
12
is transmitted to outside via the optical fiber
3
.
Reference numeral
2
refers to a receiver side LSI composed of a CMOS, a Bi-CMOS, bipolar, GaAs or the like which is a logic circuit for processing multiple electric signals separately. Here, reference numeral
22
refers to a photo-diode or a photo diode array. Reference numeral
23
refers to a receiver side optical connector. The photo diode
22
is optically coupled with the optical fiber
3
via the optical connector
23
. This photo diode
22
photoelectric-converts the optical signal, which has been transmitted from outside via the optical fiber
3
, into an electric current that corresponds to the original electric signal. The output electric current signal of the photo-diode
22
is supplied to a current-voltage conversion circuit
21
, which converts the output electric current signal of the photo-diode
22
into a voltage signal. Reference numeral
24
refers to a comparator. The voltage signal output from the current-voltage conversion circuit
21
is applied to one input terminal of the comparator
24
. A reference voltage V
ref
is applied to the other input terminal of the comparator
24
.
As has been explained above, when a signal is transmitted from the transmission side LSI
1
to the receiver side LSI
2
via the optical fiber, the output electric signal of the transmission side LSI
1
is input to the laser driver
11
. The laser diode
12
is then driven in response to the output signal of the transmission side LSI
1
. The photo diode
22
receives via the receiver side optical connector
23
the optical signal that has been transmitted via the optical connector
13
and optical fiber
3
. The photo diode
22
then generates an electric current signal pulse. The current-voltage conversion circuit
21
converts the electric current signal pulse, which has been generated by the photo-diode
22
, into a voltage signal. The comparator then
24
compares the voltage signal with the reference voltage V
ref
. The voltage signal is then input as a logic signal to the receiver side LSI
2
.
Here, the drive current-emission power characteristic of the laser diode
12
is susceptible changes in temperature. Specifically, the emission power intensity of the laser diode
12
changes as the surrounding temperature of the laser diode
12
and the amount of self-generated heat change. The change in the emission power intensity causes the timing accuracy of the transmission signal to deteriorate. The change in the power source voltage of the laser diode
12
also causes the timing accuracy to deteriorate.
SUMMARY OF THE INVENTION
Given these problems, it is an object of the present invention to provide an optical signal transmission apparatus and an optical signal transmission method capable of solving the above-stated problems. The object of the present invention can be achieved by a combination of characteristics described in the independent claims of the present invention. The dependent claims of the present invention determine further advantageous embodiments of the present invention. This invention provides a parallel optical signal transmission apparatus which has a laser diode and a photo diode, that suppresses timing jitter and drift generated by a power source noise, a drift, and changes in temperature, thereby solving the above-described problem.
According to the first aspect of the present invention, an optical signal transmission apparatus having a laser driver for amplifying an electric signal to be transmitted and an optical signal laser diode for outputting an optical signal based on the electric signal is provided. This optical signal transmission apparatus has a reference current source which outputs as a reference current a prescribed proportion of the maximum current value of the electric signal, and a reference laser diode which generates a standard reference light, driven by the reference current.
According to the second aspect of the present invention, an optical signal transmission apparatus as described in the first aspect of the present invention is provided which has a plurality of the laser drivers which output a plurality of the electric signals in parallel.
According to the third aspect of the present invention, an optical signal transmission apparatus as described in the first or second aspect of the present invention is provided such that the laser diode and the reference laser diode are structured as a laser diode array.
According to the fourth aspect of the present invention, an optical signal transmission apparatus as described in any of the first through third aspects of the present invention is provided such that the reference current source outputs as the reference current approximately ½ the maximum current value of the electric signal.
According to the fifth aspect of the present invention, an optical signal transmission apparatus as described in any of the first through fourth aspects of the present invention is provided such that the reference laser diode constantly outputs the standard reference light.
According to the sixth aspect of the present invention, an optical signal propagation apparatus is provided. This optical signal propagation apparatus has a transmission unit which converts an electric signal into an optical signal and transmits the optical signal, having a laser driver for amplifying the electric signal, an optical signal laser diode which outputs the optical signal based on the electric signal which the laser driver has amplified, a reference current source which outputs as a transmission side reference current a prescribed proportion of the maximum current value of the electric signal, and a reference laser diode which outputs a standard reference light based on the transmission side reference current. This optical signal propagation apparatus also has an optical fiber for propagating the optical signal, and a receiving unit which receives the optical signal that is propagated through the optical fiber. The receiving unit has a current signal photo diode which receives the optical signal, which has been transmitted through the optical fiber, and converts the received optical signal into a corresponding current signal, a reference current photo diode which receives the standard reference light, which has been transmitted through the optical fiber, and converts the standard reference light into a corresponding receiver side reference current, a current-voltage conversion circuit which converts the current signal and the receiver side reference current into a voltage signal and a reference voltage, respectively,
Advantest Corporation
Font Frank G.
Inzirillo Gioacchino
Pillsbury Madison & Sutro LLP
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