Coherent light generators – Raman laser
Reexamination Certificate
2000-11-06
2003-07-15
Ip, Paul (Department: 2828)
Coherent light generators
Raman laser
C372S020000, C372S022000
Reexamination Certificate
active
06594288
ABSTRACT:
TECHNICAL FIELD
The present invention relates to Raman lasers and amplifiers, and more particularly to a tunable Raman laser and amplifier using a plurality of Bragg gratings to define a cascaded resonator configuration.
BACKGROUND ART
Fiber Bragg gratings and other grating elements are finding widespread use in both telecommunications and sensing applications. Gratings have also enabled new configurations of fiber lasers and optical signal amplifiers.
Cascaded cavity Raman lasers and optical signal amplifiers, which utilize the stimulated Raman scattering (SRS) in an optical fiber, are known. Raman scattering, a non-linear optical process, is a process in which a small fraction of incident light is scattered by vibrational modes within a non-linear medium (e.g. a silica-based fiber) and is shifted by a known Stokes shift to a typically longer wavelength.
An exemplary cascaded Raman laser
10
, as shown in
FIG. 1
, has an input section
12
including four fiber Bragg gratings
14
-
17
, and an output section
18
also including four fiber Bragg gratings
20
-
23
that match the gratings in the input section, similar to that described in U.S. Pat. No. 5,323,404. Each pair of matched fiber Bragg gratings (
14
and
20
,
15
and
21
,
16
and
22
,
17
and
23
) forms an optical cavity, with the gratings having high reflectivity. Pump radiation, having a pump wavelength &lgr;
p
, propagates essentially unimpeded through the input section
12
into the optical fiber
24
, where most of the radiation will be converted by Raman scattering to radiation at a higher wavelength corresponding to a first order Stokes shift, which is then reflected within the first cavity defined by the first pair of matched fiber Bragg gratings (
14
and
20
). The reflected radiation of the first resonance cavity is then substantially converted by Raman scattering to a higher wavelength corresponding to the second order Stokes shift, which is reflected within the second cavity defined by the second pair of matched fiber Bragg gratings (
15
and
21
). The reflected radiation of the second resonance cavity is then substantially converted by Raman scattering to a higher wavelength corresponding to the third order Stokes shift, which is reflected within the third cavity defined by the third pair of matched fiber Bragg gratings (
16
and
22
). The reflected radiation of the third resonance cavity is then substantially converted by Raman scattering to a higher wavelength corresponding to the fourth order Stokes shift, which is reflected with the fourth cavity defined by the fourth pair of matched fiber Bragg gratings (
17
and
23
). This radiation at the fourth order Stokes shift is then available for utilization.
The use of fiber Bragg gratings to create a resonant cavity increases the optical power in the fiber and has allowed Raman amplification in shorter lengths of fiber. However, as a result of the relatively narrow bandwidth of the Stokes order, Raman lasers and amplifiers are not tunable over an extended wavelength range.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a tunable Raman laser and tunable Raman optical amplifier by which the lasing wavelength of the Raman laser and amplification wavelength of the Raman amplifier can be tuned to allow a more extended adjustment of the output wavelength.
In accordance with an embodiment of the present invention, a tunable Raman laser comprises a pump source that provides pump radiation having a predetermined wavelength. A first optical waveguide includes at least a pair of first reflective elements. Each of the first reflective elements has a respective reflection wavelength. A second optical waveguide includes at least a pair of second reflective elements. Each of the second reflective elements has a respective reflection wavelength, wherein each of the first reflective elements has a respective reflection wavelength substantially the same as a reflection wavelength of a corresponding one of the second reflective elements to form at least a pair of resonant cavities. An optical waveguide, which is optically coupled between the first optical waveguide and the second optical waveguide, provides Raman gain. A tuning device, responsive to a signal representative of a desired output wavelength, stresses the first and second optical waveguides to change the reflective wavelengths of the first and second reflective elements. Portions of each of the first and second optical waveguides have different cross-sectional areas such that when the first and second optical waveguides are stressed, the reflection wavelengths of the first reflective elements change proportionally and the reflection wavelengths of the second reflective elements change proportionally.
In accordance with an embodiment of the present invention, a tunable Raman optical amplifier for amplifying an input light signal having a wavelength is provided. The amplifier comprises a pump source that provides pump radiation having a predetermined wavelength. An optical coupler couples the pump radiation into the input light signal. A first optical waveguide includes at least a pair of first reflective elements. Each of the first reflective elements has a respective reflection wavelength. A second optical waveguide includes at least a pair of second reflective elements. Each of the second reflective elements has a respective reflection wavelength, wherein each of the first reflective elements has a respective reflection wavelength substantially the same as a reflection wavelength of a corresponding one of the second reflective elements to form at least a pair of resonant cavities. An optical waveguide, which is optically coupled between the first optical waveguide and the second optical waveguide, provides Raman gain. A tuning device, responsive to a signal representative of a desired output wavelength, stresses the first and second optical waveguides to change the reflective wavelengths of the first and second reflective elements. Portions of each of the first and second optical waveguides have different cross-sectional areas such that when the first and second optical waveguides are stressed, the reflection wavelengths of the first reflective elements change proportionally and the reflection wavelengths of the second reflective elements change proportionally.
REFERENCES:
patent: 4725110 (1988-02-01), Glenn et al.
patent: 4807950 (1989-02-01), Glenn et al.
patent: 4915467 (1990-04-01), Berkey
patent: 5007705 (1991-04-01), Morey et al.
patent: 5042898 (1991-08-01), Morey et al.
patent: 5235659 (1993-08-01), Atkins et al.
patent: 5258988 (1993-11-01), Whittley
patent: 5265106 (1993-11-01), Garcia et al.
patent: 5293394 (1994-03-01), Whittley
patent: 5323404 (1994-06-01), Grubb
patent: 5388173 (1995-02-01), Glenn
patent: 5469520 (1995-11-01), Morey et al.
patent: 5691999 (1997-11-01), Ball et al.
patent: 5745626 (1998-04-01), Duck et al.
patent: 5815518 (1998-09-01), Reed et al.
patent: 5838700 (1998-11-01), Dianov et al.
patent: 5912910 (1999-06-01), Sanders et al.
patent: 5966480 (1999-10-01), LeGrange et al.
patent: 6122096 (2000-09-01), Fatchi
patent: 6229827 (2001-05-01), Fernald et al.
patent: 6229828 (2001-05-01), Sanders
patent: 6310990 (2001-10-01), Putnam et al.
patent: 6344925 (2002-02-01), Grubb et al.
patent: 6363089 (2002-03-01), Fernald et al.
patent: 0954072 (1999-11-01), None
patent: 0984532 (2000-03-01), None
patent: WO 8204328 (1982-12-01), None
patent: WO 9530926 (1995-11-01), None
patent: WO 0037969 (2000-06-01), None
patent: WO 0039617 (2000-07-01), None
patent: WO 0049721 (2000-08-01), None
Kersey Alan D.
Putnam Martin A.
CiDRA Corporation
Ip Paul
Nguyen Tuan
LandOfFree
Tunable raman laser and amplifier does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Tunable raman laser and amplifier, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tunable raman laser and amplifier will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3004789