Laser driver circuit and system

Details Laser driver circuit and system Laser driver circuit and system

2002-07-11

2004-06-01

Porta, David (Department: 2878)

Coherent light generators

Particular component circuitry

For driving or controlling laser

C372S038070

Reexamination Certificate

active

06744795

ABSTRACT:

BACKGROUND
1. Field
The subject matter disclosed herein relates to data communication systems. In particular, the subject matter disclosed herein relates to transmitting data in an optical transmission medium.
2. Information
Data transmission in an optical transmission medium such as fiber optic cabling has enabled communication at data rates of 10 gigabits per second and beyond according to data transmission standards set forth in IEEE P802.3ae and Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) published by the International Telecommunications Union (ITU). To transmit data in the optical transmission medium, a laser device typically modulates an optical signal using wave division multiplexing (WDM) in response to a data signal.
FIG. 1
shows a schematic diagram of a prior art laser driver circuit
50
to provide a modulation current
60
to a laser device
58
. The laser device circuit may be formed in a single complementary metal oxide semiconductor (CMOS) device. The laser device
58
receives a modulation current
60
to power the transmission of an optical signal
62
in an optical transmission medium. The laser device
58
typically also modulates the optical signal in response to a data signal. The laser driver circuit receives a reference current
52
generated by, for example, a controlled voltage source applied across an off-chip resistor. A diode coupled field effect transistor (FET)
54
and FET
56
form a current mirror to generate the modulation current
60
at a magnitude that is substantially proportional to the magnitude of the input reference current
52
. Short channel lengths in such a CMOS device may introduce channel length modulation effects, causing nonlinearities in the output modulation current
60
(e.g., affecting the ratio of the reference current
52
to the modulation current
60
). The resulting magnitude of the modulation current
60
, therefore, may not be sufficiently accurately generated for high data rate communication in an optical transmission medium.


REFERENCES:
patent: 6389050 (2002-05-01), Stronczer
patent: 6392215 (2002-05-01), Baumgartner et al.
patent: 6532245 (2003-03-01), Paschal et al.
patent: 6587489 (2003-07-01), Schrodinger
Design of Analog CMOS Integrated Circuits, Behzad Razavi, 2001, pp. 393 and 394.
IEEE P802.3ae, Apr. 15, 2002, clauses 46-48.

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