Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1997-07-22
1999-09-28
Negash, Kinfe-Michael
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359128, H04J 1400
Patent
active
059597488
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Modern, futuristic optical trunk traffic networks have to satisfy stringent requirements in terms of capacity, flexibility, reliability and transparency. These requirements for a transport network are optimally satisfied when data are transmitted and switched using the optical frequency division multiplex method. In the case of the optical frequency-division multiplex method (wavelength-division multiplex--WDM), a plurality of transmission channels are combined on one fiber and are separated from one another by their optical carrier frequencies (wavelengths) which differ from one another by several 100 GHz. The maximum number of possible channels in this case limited by the amplification bandwidth of optical fiber amplifiers.
Optical cross-connects (OCC) are provided for semi-permanent and blocking-free coupling of optical channels. Such optical cross-connects, as a rule, have both a frequency switching stage and a space division switching stage.
ICC'93 Conf.Rec. Vol.3/3, 1300 . . . 1307, FIG. 10, in this context discloses a WDM switching arrangement having wavelength demultiplexers on the input side which in each case split the incoming optical signal on the associated input fiber on the basis of wavelengths, a downstream space division switching arrangement (space switch), downstream adjustable wavelength converters which convert the respectively incoming wavelength to the respective outgoing wavelength, and wavelength multipliers on the output side which combine the wavelengths supplied to them.
ntz 46(1993)1, pages 16 . . . 21, FIGS. 13 and 14 discloses WDM switching arrangements in which wavelength demultiplexers (1/N in FIG. 13; unnamed in FIG. 14) are likewise provided on the input side, wavelength multiplexers (N/1 in FIG. 13; unnamed in FIG. 14) are provided on the output side, and wavelength converters (frequency stages in FIG. 13; filter and frequency converters in FIG. 14) are provided for wavelength conversion to the respective outgoing wavelength, with an intermediate space division switching arrangement (space stage in FIG. 13; fiber switch in FIG. 14) is also provided.
In such arrangements of optical (de)multiplixers and space division switching arrangement the same optical frequency (wavelength) may possibly always be applied to each input of the space division switching arrangement, in which case, with the same frequency allocation of the individual optical waveguides in each case to the same frequency division multiplex of M optical carrier frequencies, the optical frequency of an input of the space division switching arrangement is repeated every M inputs.
The object of the space division switching arrangement is to connect the inputs to the outputs without any blocking, that is to say to make it possible to switch a path through the space division switching arrangement, in every load case, between any given free input and any given free output.
One possible architecture for a space division switching arrangement having N inputs and N outputs is a combination of in each case N 1xN tree structures at the N inputs and N outputs with a link network (shuffle network) between the tree structures of the inputs and outputs; in this case, each tree structure can be formed by a pyramid of 1x2 switches (see, for example, JP-A-61194408, JP-A-62020493).
Technical implementations of optical 1x2 switches in fact have only a limited amount of crosstalk attenuation: some of the respective signal also passes to that output which is not currently selected, which has the effect of crosstalk between one signal path and another signal path in the space division switching arrangement. The crosstalk attenuation of currently available optical switches based on semiconductors is still unsatisfactory, and a space division switching arrangement which is formed from such switches therefore does not per se satisfy the system requirements. In this case, crosstalk between two channels at the same optical frequency is particularly critical while, in the case of a crosstalk signal at a diff
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Patent Abstracts of Japan, JP62-020493, vol. 11, No. 195 (E-518), Jan. 29, 1987, Suzuki Shuji, Control System for Optical Switch Network.
Patent Abstracts of Japan, JP61-194408, vol. 11, No. 19 (P-537) Aug. 28, 1986, Habara Takashi, Optical Switch Matrix.
Applied Optics, vol. 14, No. 11, Nov. 1975, New York, R.A. Soref et al, Crosstalk Reduction in Optical Switching, pp. 2559-2560.
ICC Conference Record, Geneva, 1993, vol. 3/3, Communications--Technology that Unites Nations, Ken-ichi Sato et al, Optical Path Layer Technologies to Enhance B-ISDN Performance, pp. 1300-1307.
ntz 46 (1993) vol. 46, Ernst-Juergen Bachus et al, Optische Frequenzmultipextechnik, pp. 16-20.
Electronics Letters, vol. 30, No. 3, Feb. 3, 1994, B. Acklin et al, Novel Optical Switches Based on Carrier Injection in Three and Five Waveguide Couplers: TIC and SIC, pp. 217-218.
Negash Kinfe-Michael
Siemens Aktiengesellschaft
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