Coherent light generators – Particular beam control device – Mode locking
Patent
1994-01-12
1995-01-10
Scott, Jr., Leon
Coherent light generators
Particular beam control device
Mode locking
372 26, 372 12, 372 6, H01S 3098
Patent
active
053814266
DESCRIPTION:
BRIEF SUMMARY
Under many circumstances in the telecommunications field it is desirable to obtain pulse laser emissions of a particularly limited duration.
Pulses of the above kind having a duration .delta.t<100 ps, commonly referred to as very short pulses or "solitons" (under guided propagation conditions), apply in particular to high speed digital telecommunications (up to 10 GBit/s) and in addition to the accomplishment of optical instruments, tests on semiconductor components and also to remote measurements, in topography or in the atmospheric radar field for example.
To this end, mode-locking pulse laser generators are known; by mode-locking it is meant a process by which, in a laser, several modes oscillate in a mutual constant-phase relationship, by effect of a non-linear-behaviour element present in the laser cavity.
Mode-locking laser generators of the passive type are known which comprise optical-fibre laser devices using erbium doped fibres (the laser shown in FIG. 8, for example) in which a fibre ring containing an optical amplifier, acts as a saturable absorber, for example to the wavelength of 1.5 .mu.m; pulses generated in these lasers depend on the laser ring size.
Devices of the above kind are described for example in ELECTRONICS LETTERS, vol. 26, No. 6, Mar. 14, 1991 p. 542-543, by D. J. Richardson, R. I. Laming, D. N. Payne, V. Matsas, M. W. Phillips, in ELECTRONICS LETTERS, vol. 27, No. 9, Apr. 25, 1991, p. 730-732, by the same authors, in ELECTRONICS LETTERS, vol. 27, No. 6, Mar. 14, 1991, p. 544-545, by I. N. Duling and in ELECTRONICS LETTERS, vol. 27, No. 3, Jan. 31, 1991, p. 229-230, by G. J. Cowle and D. N. Payne.
Optical-fibre laser devices are also known in which an active modulation device of the electro-optical type is inserted in an optical path forming a laser cavity so as to force the laser to generate mode-locking pulses at the desired frequency.
Such devices are referred to as active mode-locking devices because the modulation device present therein operated from the outside acts on the modes generated in the laser, enabling amplification up to a level keeping the laser emission to the only modes selected by the applied modulation.
Devices of the above type are described for example in OPTICS LETTERS, vol. 14, No. 22, Nov. 15, 1989, p. 1269-1271, by J. D. Kafta, T. Baer and D. W. Hall, in ELECTRONICS LETTERS, vol. 26, No. 3, Feb. 1, 1990, p. 216-217, by A. Takada and H. Miyazawa, in CLEO '92 Anaheim, Paper CW14, by C. Harvey and L. Mollenauer, and in PROCEEDINGS OF II TOPICAL MEETING ON OPTICAL AMPLIFIERS, Optical Society of America, 1991, Snowmass Village, Colo., USA, p. 116-119, by T. Pfeiffer and H. Schmuck (SEL Alcatel Research Centre).
Theoretical foundations for mode-locking both of the active and passive type are shown, for example, in WAVES AND FIELDS IN OPTOELECTRONICS, by Herman A. Haus, issued in 1984 by Prentice-Hall, Inc., Englewood Cliffs, N.J., p. 254-290.
Passive mode-locking generators the operation of which leaves out of consideration an exciting modulation, have the particular feature that they have a soliton-pulse emitting frequency closely depending on the physical features of the generator, in particular the sizes of the fibre ring forming the laser system, in which for each reflection a single pulse travels.
In active mode-locking generators, on the contrary, the pulse emitting frequency depends on the exciting frequency of a modulator and it enables a great number of locked pulses simultaneously travelling in the ring to be present and therefore enables the pulse emitting frequency to be previously selected and to be much higher than in the passive-type devices, on the order of GHz for example.
In addition to the foregoing, mode-locking laser generators can be provided with a filter adapted to enable selection of the emission wavelength of the emitted pulses within a given frequency band, in the 1530-1560 nm band for example, which is the band commonly used in telecommunications, both for feeding different sources on the same fibre and for adaptation to the ch
REFERENCES:
patent: 4904041 (1990-02-01), Izadpanah
patent: 5054027 (1991-10-01), Goodberlet et al.
patent: 5200964 (1993-04-01), Huber
patent: 5210631 (1993-05-01), Huber et al.
patent: 5243610 (1993-09-01), Murata
patent: 5285309 (1994-02-01), Endoh et al.
patent: 5309453 (1994-05-01), Treacy
Proceedings II Topical Meeting on Optical Amplifiers, OSA, 1991 Snowmass Village, Co., USA pp. 116-119.
Optics Letters, vol. 16, No. 6, 15 Mar. 1991, New York US, pp. 387-389.
Patent Abstracts of Japan-vol. 016, No. 451 18 Sep. 1992 & JP-A-41 59 516 (NEC Corp) 2 Jun. 1992 Abstract.
Patent Abstracts of Japan-vol. 016, No. 053 10 Feb. 1992 and JP-A-32 52 618 (Fujitsu Ltd.) 11 Nov. 1991 Abstract.
Electronics Letters vol. 28, No. 14, 2 Jul. 1992 Enage GB pp. 1291-1293, F. Fontana et al.
Bosso Sergio
Fontana Flavio
Jr. Leon Scott
Pirelli Cavi S.p.A.
LandOfFree
Active-mode-locking optical-fiber laser generator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Active-mode-locking optical-fiber laser generator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Active-mode-locking optical-fiber laser generator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-856461