Coherent light generators – Particular beam control device – Optical output stabilization
Reexamination Certificate
1999-01-11
2001-08-07
Kim, Robert H. (Department: 2877)
Coherent light generators
Particular beam control device
Optical output stabilization
C372S031000, C372S034000, C372S103000, C372S020000, C372S028000, C372S101000, C372S029011, C372S027000, C372S009000
Reexamination Certificate
active
06272157
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to the field of wavelength stabilized laser systems.
DESCRIPTION OF THE RELATED ART
The wavelength stabilized laser is a recently developed component of dense wavelength division multiplexed (DWDM) systems. In a DWDM system, a single semiconductor laser device may be used to provide light at several predetermined wavelengths (each corresponding to a different channel.) Commercial devices have been produced with 100 gigahertz spacing. If it becomes necessary to add further channels to an existing optical fiber, even denser wavelength spacing may be used in the future. As the wavelength spacing decreases, wavelength stabilization takes on a more important role.
U.S. Pat. No. 5,832,014 to Johnson, which is assigned to Lucent Technologies Inc., is incorporated herein by reference in its entirety for its teachings on wavelength stabilization in tunable semiconductor lasers. Johnson describes a tunable semiconductor laser including a gain section and at least one tuning section. Spontaneous emission (SE) from the tuning section is detected and used in a feedback control loop to control the amount of current applied to the tuning section. The feedback control loop operates to maintain the detected SE at a constant level, such that the current applied to the tuning section is adjusted to compensate for the effects of aging and the laser output wavelength is thereby stabilized.
Johnson rejects a number of alternative approaches, stating that, “Conventional approaches to solving the wavelength stabilization problem in tunable semiconductor lasers generally involve monitoring the lasing wavelength using precise filters . . . . However, these filtering techniques can be expensive and difficult to implement in many practical applications. Moreover, the required filters are often unsuitable for integration with the semiconductor laser on a single chip.”
A method and apparatus are desired that makes use of filters for wavelength stabilization in semiconductor lasers practical and effective.
SUMMARY OF THE INVENTION
The present invention is a calibration apparatus and method in which a window is provided in the laser housing, and an electromagnetic radiation source outside of the housing transmits a calibration beam through the window and through the filter, onto a detector.
The calibration apparatus includes a first detector that monitors an amplitude of a laser light output by the laser. A filter receives the laser light and outputs a filtered light having an amplitude that varies with the wavelength of the laser light. A second detector monitors the amplitude of the filtered light. A sealed housing contains the first and second detectors and the filter. The housing has a window. An electromagnetic radiation source outside of the housing transmits a calibration beam through the window and through the filter, onto the second detector.
REFERENCES:
patent: 4901306 (1990-02-01), Gardner
patent: 4912526 (1990-03-01), Iwaoka et al.
patent: 4914662 (1990-04-01), Nakatani et al.
patent: 5084884 (1992-01-01), Terada
patent: 5384799 (1995-01-01), Osterwalder
patent: 5428700 (1995-06-01), Hall
patent: 5764678 (1998-06-01), Tada
patent: 5786915 (1998-07-01), Scobey
patent: 5832014 (1998-11-01), Johnson
Tidrow et al., “A high strain two-stack two-color quantum well infrared photodetector”, Appl. Phys. Lett. 70(7):859-861, Feb. 1997.
Chen et al., “Two-color corrugated quantum-well infrared photodetector for remote temperature sensing”, Appl. Phys. Lett. 72(1):7-9, Jan. 1998.
1998 Santec Component Series, pp. 1-11.
Wavelength-Selected (D2526G) Laser 2000 Direct Modulated Isolated DFB Laser Module, Lucent Technologies, Bell Labs Innovations, Aug. 1997, pp. 1-8.
Wavelength Locker Test Report, JDS Fitel, Dec. 4, 1997, pp. 1-3.
Nortel Networks: Optical Networking/Transport, Nov. 18, 1998, pp. 1-3.
Broadband: Product Portfolio—Utility Networks, Nortel, Nov. 18, 1998, pp. 1-2.
News Letter, 32ch Tunable Laser Light Source System, Nov. 18, 1998, p. 1.
News Letters, Optical Variable Attenuator, OVA-630, Nov. 18, 1998, p. 1.
Components for DWDM Systems, Santec, Laser Focus World, Oct. 1998, p. 70.
Broutin Scott L.
Plourde James Kevin
Przybylek George John
Stayt, Jr. John William
Walters Frank Stephen
Agere Systems Optoelectronics Guardian Corp.
Duane Morris & Heckscher LLP
Flores Ruiz Delma R.
Kim Robert H.
Koffs Steven E.
LandOfFree
Apparatus and method for calibrating a wavelength stabilized... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for calibrating a wavelength stabilized..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for calibrating a wavelength stabilized... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2515668