Optical receiver and optical transmission system using the receiver
First Claim
1. An optical frequency shift keying (FSK) receiver for use in an optical frequency division multiplexing (FDM)-FSK transmission system, said receiver comprising:
- light splitting means for splitting an optical FSK signal into at least two light portions;
at least two tunable optical filters, said filters respectively receiving the light portions from said light splitting means and being respectively capable of changing their transmission wavelengths;
at least two light receiving means for receiving lights from said filters, respectively, said light receiving means respectively supplying electrical signal outputs; and
producing means for producing a difference signal from the outputs of said light receiving means;
wherein mark and space optical frequencies of one optical FSK signal split by said light splitting means are respectively transmitted through said tunable optical filters whose transmission wavelengths are respectively tuned to the mark and space optical frequencies, the transmitted mark and space optical frequencies are directly and independently received by said light receiving means and the optical FSK signal is received by using the difference signal produced by said producing means.
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Abstract
In an optical receiver of the present invention, an optical signal is split into at least two light portions, and the light portions are respectively received by at least two tunable optical filters. The tunable optical filters are respectively capable of changing their transmission wavelengths. Transmitted lights through the tunable optical filters are received by at least two light receiving elements. The light receiving elements respectively supply outputs. A differential amplifier produces a difference signal from the outputs of the light receiving elements. In an optical FDM-FSK transmission system using the optical receiver, an optical FSK signal is received by utilizing the difference signal. The tracking operation of the tunable optical filters, whose object includes, for example, at least a center optical frequency of the tunable filters, can be readily performed.
66 Citations
25 Claims
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1. An optical frequency shift keying (FSK) receiver for use in an optical frequency division multiplexing (FDM)-FSK transmission system, said receiver comprising:
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light splitting means for splitting an optical FSK signal into at least two light portions; at least two tunable optical filters, said filters respectively receiving the light portions from said light splitting means and being respectively capable of changing their transmission wavelengths; at least two light receiving means for receiving lights from said filters, respectively, said light receiving means respectively supplying electrical signal outputs; and producing means for producing a difference signal from the outputs of said light receiving means; wherein mark and space optical frequencies of one optical FSK signal split by said light splitting means are respectively transmitted through said tunable optical filters whose transmission wavelengths are respectively tuned to the mark and space optical frequencies, the transmitted mark and space optical frequencies are directly and independently received by said light receiving means and the optical FSK signal is received by using the difference signal produced by said producing means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. An optical FDM-FSK transmission system for communicating over a light transmission line that transmits signal lights, said system comprising:
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(a) signal transmitting means for transmitting an optical FSK signal; and (b) an optical FSK receiver, said receiver comprising; light splitting means for splitting the optical FSK signal into at least two light portions; at least two tunable optical filters, said filters respectively receiving the light portions from said light splitting means and respectively comprising means for changing their transmission wavelengths; at least two light receiving means for receiving lights from said filters, respectively, said light receiving means respectively supplying electrical signal outputs; and producing means for producing a difference signal from the outputs of said light receiving means; wherein mark and space optical frequencies of one optical FSK signal split by said light splitting means are respectively transmitted through said tunable optical filters whose transmission wavelengths are respectively tuned to the mark and space optical frequencies, the transmitted mark and space optical frequencies are directly and independently received by said light receiving means and the optical FSK signal is received by using the difference signal produced by said producing means. - View Dependent Claims (23, 24, 25)
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Specification