Optical wavelength converter based on cross-gain modulation...

Details Optical wavelength converter based on cross-gain modulation... Optical wavelength converter based on cross-gain modulation...

1999-10-12

2003-06-10

Stafira, Michael P. (Department: 2877)

Optical: systems and elements

Optical frequency converter

C359S344000, C359S336000, C359S341430, C372S038060, C372S020000, C372S075000

Reexamination Certificate

active

06577435

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an optical wavelength converter. More particularly, the present invention relates to an optical wavelength converter based on cross-gain modulation with wide input power dynamic range.
BACKGROUND OF THE INVENTION
Wavelength converters are the key elements in wavelength division multiplexed (WDM) networks and photonic switch blocks. They are the devices that convert the wavelength of optical transmission signals independently of transmission speed and transmission system. One important use is to avoid wavelength blocking in optical cross connects in WDM networks. Therefore, the converters increase the flexibility and the capacity of the network for fixed wavelengths. Among the wavelength conversion methods, cross-gain modulation (XGM), cross-phase modulation (XPM), and four-wave mixing (FWM) in semiconductor optical amplifiers (SOA's) have been widely studied and investigated. Wavelength converters by XGM in SOA's have the advantages of simple structure and high conversion efficiency. However, disadvantages include the extinction ratio degradation after conversion, the inversion of bit-stream, and the narrow input power dynamic range.
FIG. 1
shows a diagram for illustrating a conventional optical wavelength converter using cross-gain modulation.
As shown in
FIG. 1
, the intensity-modulated input signal beam at &lgr;
S
and continuous wave beam at &lgr;
C
are injected into a semiconductor optical amplifier
13
. The input signal beam is the pump beam
15
, and the continuous wave beam is the probe beam
16
. The intensity of the continuous wave beam, i.e., probe beam
16
, depends upon the amount of bias current loaded to the continuous wave source
12
from the current driver
11
.
The operation principle relies on gain saturation in the semiconductor optical amplifier
13
. A strong pump beam
15
is used to modulate the gain of the semiconductor optical amplifier
13
. A probe beam
16
at desired wavelength is modulated according to the bit pattern of the pump beam
15
due to the effect of gain modulation. At the output, the wavelength converted beam is obtained by passing only the probe beam through a band pass filter
14
. Therefore, the wavelength of the input signal, &lgr;
S
is converted into the desired wavelength, &lgr;
C
.
Conventional optical converters using cross-gain modulation have several drawbacks. For example, the extinction ratio of the wavelength converted beam is low and bit stream is inversed. In addition, input power dynamic range is narrow.
SUMMARY OF THE INVENTION
The present invention provides an optical wavelength converter based on cross-gain modulation with wide input power dynamic range. An optical wavelength converter based on cross-gain modulation with wide input dynamic range in accordance with the present invention comprises a semiconductor optical amplifier, a continuous wave source, and a probe beam controller. The semiconductor optical amplifier modulates probe power on the basis of pump power. The continuous wave source generates the probe beam and supplies generated probe beam to the semiconductor optical amplifier. The probe beam controller supplies adequate bias current to the continuous wave source and the probe power changes in accordance with the pump power.


REFERENCES:
patent: 5264960 (1993-11-01), Glance
patent: 5450229 (1995-09-01), Wiesenfeld
patent: 5721637 (1998-02-01), Simon et al.
Joergensen et al., “4 Gb/s Optical Wavelength Conversion Using Semiconductor Optical Amplifiers,”IEEE Photonics Technology Letters, 5(6):657-660, 1993.
Wiesenfeld et al., “Wavelength Conversion at 10 Gb/s using a Semiconductor Optical Amplifier,”IEEE Photonics Technology Letters, 5(11):1300-1303, 1993.
Chelles et al., “Extinction Ratio of Cross-Gain Modulated Multistage Wavelength Converters: Models and Experiments,”IEEE Photonics Technology Letters, 9(6):758-760, 1997.

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