Optics: measuring and testing – Range or remote distance finding – With photodetection
Patent
1987-02-18
1988-11-22
Sikes, William L.
Optics: measuring and testing
Range or remote distance finding
With photodetection
350354, 356345, G02B 626
Patent
active
047861290
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an optical coupling assembly for controlling the coupling of an input optical signal between an input port and a pair of output ports.
In accordance with one aspect of the present invention, an optical coupling assembly comprises a conversion device to which an optical control signal and an input signal are fed, the conversion device being responsive to changes in amplitude of the control signal to produce corresponding phase shifts in the input signal; and optical coupling means having two input ports and two outputs ports for coupling the phase shifted input signal from the conversion device with the input signal the arrangement being such that the proportion of the input signal output from each output port of the optical coupling means is selectable by controlling the amplitude of the control signal.
SUMMARY OF THE INVENTION
The invention provides a neat way in which to couple an optical input signal selectively with one of two output ports.
In one arrangement the control signal component could be separated from the phase shifted signal prior to the one coupling means by the insertion of suitable separation means in the signal path.
Preferably, the assembly includes additional optical coupling means having two input ports and two output ports, the two output ports being connected respectively with the conversion device and an input port of the one optical coupling means and the two input ports receiving, in use, the control signal and the input signal respectively.
In this case proportions of both the control signal and non-phase shifted input signal will be fed to the one coupling means. To deal with this, separation means could be inserted between the coupling means or downstream of the one coupling means to remove the control signal component if desired.
The conversion device is preferably provided by an optical device which has a refractive index which varies in accordance with the optical power of the optical control signal. This variation causes changes in the optical path length through the device. An example of a suitable conversion device is a semiconductor laser amplifier.
In accordance with a second aspect of the present invention, a method of operating an optical coupling assembly according to the one aspect of the invention comprises generating a control signal having one of two amplitudes, the power of the control signal being such that the input signal is substantially completely coupled with one of the two output ports of the one coupling means, the output port being selected in accordance with the amplitude of the control signal.
In this way, the optical coupling assembly is used as an optical switch.
Preferably, the control signal has a different wavelength from the input signal. This simplifies the filtering out of the control signal downstream of the optical coupling means which is necessary in certain applications.
In this specification, the term optical is intended to refer to that part of the electromagnetic spectrum which is generally known as the visible region together with those parts of the infra-red and ultra-violet regions at each end of the visible region which are capable of being transmitted by dielectric optical waveguides such as optical fibres.
BRIEF DESCRIPTION OF THE DRAWINGS
Some examples of optical switches in accordance with the present invention will now be described with reference to the accompanying drawings, in which:
FIG. 1 illustrates a first example of an optical coupling assembly in accordance with the present invention;
FIG. 2 illustrates a second example of an optical coupling assembly in accordance with the present invention; and
FIG. 3 illustrates a third example of an optical coupling assembly in accordance with the present invention.
DETAILED DESCRIPTION
The switch shown in FIG. 1 comprises a first optical fibre coupler 1 having two input ports defined by optical fibres 2, 3 and two output ports defined by optical fibres 4, 5. The optical fibre 4 is connected to a semiconductor laser amplifie
REFERENCES:
patent: 3691387 (1972-09-01), DeLange
patent: 3908121 (1975-09-01), Riseberg et al.
patent: 4552457 (1985-11-01), Giallorenzi et al.
Wyatt et al., Electronics Letters, vol. 19, No. 14, 7 Jul. 1983, "1.52 .mu.m PSK Heterodyne Experiment Featuring an External Cavity Diode Laser Local Oscillator", pp. 550-551.
Kobayashi et al., Electronics Letters, vol. 18, No. 5, 4 Mar. 1982, "Optical Phase Modulation in an Injection Locked AlGaAs Semiconductor Laser", pp. 210-211.
Kist et al., Laser and Optoelectronic, vol. 16, No. 1, Feb. 1984, "Fiber and Integrated Optical Monomode Sensors: A Review", pp. 17-30.
British Telecommuncations
Gonzalez Frank
Sikes William L.
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