Optical waveguides – With optical coupler – Plural
Reexamination Certificate
1999-09-13
2001-02-13
Ullah, Akm E. (Department: 2874)
Optical waveguides
With optical coupler
Plural
Reexamination Certificate
active
06188817
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the field of photonics and in particular to arrangements for controlling, routing or switching optical signals by wavelength selection.
An optical circulator as illustrated by way of example in
FIG. 1
is a known photonic device for the unidirectional transmission of an optical signal or beam from one port to the next sequential port (i.e. from port
1
to port
2
,
2
to
3
,
3
to
4
, etc), without allowing transmission in the reverse directions (i.e.
2
to
1
,
3
to
2
,
4
to
3
, etc). Thus light input at port
1
is output at port
2
, light input at port
2
is output at port
3
, etc. Here the term “light” is used to include both visible and non-visible radiation e.g. optical signals suitable for the purposes of photonics. To operate on several beams, as is necessary when handling signals from multiple optical fibres, several optical circulators are conventionally required. To perform an all-optical add-drop function that separates channels carried on different wavelengths in an optical signal (i.e. wavelength division multiplexing (WDM) wavelength channels), would also require a multiplicity of optical circulators.
With the spread of WDM wherein a plurality of wavelength channels is carried by a single optical fibre, the need for a compact and cheap means for independently operating on large numbers of wavelength channels is becoming more acute.
A requirement in wavelength multiplexed multi-channel optical networks is to have fully flexible optical add-drop and cross connect functionality at nodes of the network. This means that any wavelength channel carrying data to that node can be dropped into any one of a number of receivers at that node and that any of the node's transmitters may reuse that wavelength to send data on from that node.
To achieve these functions requires switching and demultiplexing of the WDM wavelength channels. Tuneable reflective optical gratings can be used with optical circulators to sort a signal comprising WDM wavelength channels into two sets of wavelength channels. To carry out the add-drop function with 8, 16, 32 or more channels requires the sorting function to be repeated many times which requires the use of large numbers of filters and optical circulators.
SUMMARY OF THE INVENTION
The present invention provides a photonics system comprising an optical circulator, comprising a plurality of ports; a first port arranged to receive a plurality of spatially separate optical signals each comprising a plurality of wavelengths, the plurality of optical signals arranged to produce an array of spatially separate sources of light at the first port; the optical circulator arranged to pass the plurality of optical signals to a second port; a focussing means provided at the first port to produce at the second port an array of spatially separate images of the sources of light; a plurality of optical wavelength filters arranged at the second port, in which each of the plurality of optical wavelength filters is arranged to align with a different one of the plurality of optical signals at the second port, each of the plurality of optical wavelength filters for selectively reflecting a selection of the plurality of wavelengths comprised in the respective optical signal and selectively passing others of the plurality of wavelengths.
The present invention further provides a photonics system comprising a second optical circulator, and a plurality of further filters provided at certain ports of the second optical circulator for performing a similar function to the first optical circulator in which the first optical circulator and the second optical circulator are arranged in communication with each other so that optical signals issuing from a selected port of the first optical circulator enter the second optical circulator at an input port thereof.
The present invention further provides an optical network comprising the photonics system of the invention.
The present invention further provides a telecommunications network comprising the photonics system of the invention.
The present invention further provides a photonics system comprising an optical circulator, comprising a plurality of ports, a first port arranged to receive a plurality of spatially separate optical signals each comprising a plurality of wavelengths the optical circulator arranged to pass the plurality of optical signals to a second port, to produce a plurality of spatially separate optical signals at the second port; a plurality of optical wavelength filters arranged at the second port, in which each of the plurality of optical wavelength filters is arranged to align with a different one of the plurality of optical signals at the second port, each of the plurality of optical wavelength filters for selectively reflecting a selection of the plurality of wavelengths comprised in the respective optical signal and selectively passing others of the plurality of wavelengths.
REFERENCES:
patent: 4991938 (1991-02-01), Buhrer et al.
patent: 5388001 (1995-02-01), Okayama et al.
patent: 5606439 (1997-02-01), Wu
patent: 5654812 (1997-08-01), Suxuki
patent: 5946129 (1999-08-01), Xu et al.
Tunable fibre bandpass filter based on a linearly chirped fibre Bragg grating for wavelength demultiplexing, M.G. Xu, et al., Electronic Letters, Sep. 26, 1996, vol. 32, No. 20, pp. 1918-1919.
Fiber Gratings and Applications, James R. Onstott, 3M Company, Presider, P. 106, Cleo'97, Tuesday Afternoon.
Fibre Bragg gratings tuned and chirped using magnetic fields, J.L. Cruz, et al., Electronics Letters, Jan. 30, 1997, vol. 33, No. 3, pp. 235-236.
Combining gratings and filters reduces WDM channel spacing, J.J. Pan, et al., Optoelectronics World, Sep. 1998, pp S11-S17.
8-Channel Tunable Drop Device With Thermal Tuning for 100 GHz Channel Spacing, T. Eftimov, et al., JDS Fitel, Inc., 2 pages.
Evaluation of an Optical Boosted Add/Drop Multiplexer OBADM including circulators and fiber grating filters, Proc. 21stEur. Conf. on Opt. Comm. (ECOC'95—Brussels), pp. 47-50.
Kirschstein et al.
Marconi Communications Limited
Ullah Akm E.
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