 Production of holograms |
| We claim: 1. A method of preparing a hologram which is of the silver halide in gelatin binder type ... |
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| Silver halide photographic material |
| OF THE INVENTION In the present invention, elution of an antifoggant from a silver halide emulsion ... |
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| Methods and apparatus for making holograms |
| OF PREFERRED EXEMPLARY EMBODIMENTS In the context of the present invention, a volumetric data set ... |
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| Wide image scanner |
| Accordingly, it is an object of the present invention to provide a wide image scanner which can ... |
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| Holographic optical element for optical disk pickup head |
| OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a pickup head 20, showing selected components by ... |
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| Scanning of images |
| It is therefore an object of the present invention to be able to scan all records simultaneously to ... |
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| Fax machine with retractable drawer |
| The invention may comprise a modular fax machine having a document feeder and a control panel ... |
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| Transmissive holographic optical element on aberrating substrate |
| What is claimed is: 1. A method for using a transmissive holographic optical element comprising the ... |
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| Method of preparing a hologram using readily available light sources |
| Therefore according to the present invention as a first step there is provided a method of ... |
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Demodulation technique for coherence multiplexed optical data transmission system
| Details |
Inventors: Coleman, Jeffrey O.;
Assignee: The Boeing Company (Seattle, WA)
Primary Examiner: Griffin; Robert L.
Assistant Examiner: Telesz, Jr.; Andrew J.
Attorney, Agent or Firm: Christensen, O'Connor, Johnson & Kindness
An improved demodulator and demodulation method usable in a coherence multiplexed, optical data transmission system. The demodulator comprises an interferometer and a signal processor. The interferometer has first and second arms having first ends coupled to receive radiation from an optical bus, and second ends connected to the signal processor. The path length difference between the arms is selected to approximately match that of a corresponding modulator, to within the coherence length of the optical carrier. The signal processor processes the optical signals emerging from the arms in combination, to produce a pair of electrical ouput signals. Linearly independent pairs of electrical ouput signals are produced for any two modulation signals that do not produce modulator optical path length differences that differ from one another by an integral multiple of a half wavelength of the optical carrier. In a preferred embodiment, the electrical output signals correspond to the cosine and sine of the phase modulation angle produced in the associated modulator. |
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DETAILED DESCRIPTION The present invention provides a coherence multiplexed optical data transmission system having a new demodulator that provides an increased data carrying capacity relative to prior coherence multiplexed systems.
Alternatively, the present invention provides a demodulator and demodulation method that can replace the demodulator and demodulation method of a lower capacity coherence multiplex system.
In such a modified system, the critical adjustment of the demodulator can be accomplished by electronic means, rather than by optical means as with prior demodulators.
The improved demodulator and demodulation method are for use in an optical data transmission system that includes a modulator associated with the demodulator, the modulator including means for receiving an optical carrier signal having a coherence length, and interferometer means.
The interferometer means includes modulated and reference arms, each having input and output ends, and means for coupling the optical carrier signal into the input ends of the arms.
Radiation from the output ends of the arms is coupled into an optical bus.
The optical path length of the modulated arm is varied, based upon an electrical modulation signal representing an input data channel.
For each of a plurality of modulation signal values, the modulated and reference arms have a modulator optical path length difference that exceeds the coherence length of the optical carrier signal.
For use in such a system, the demodulator comprises an interferometer, and signal processing means.
The interferometer has first and second arms each having first and second ends, and means for coupling radiation from the optical bus into the first ends of the first and second arms.
The first and second arms have a demodulator optical path length difference selected such that for each modulation signal value input to the associated modulator, the difference between the modulator and demodulator optical path length differences is less than the coherence length of the optical carrier signal
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Optical Systems 
