Optical communication system
First Claim
1. A communication system in which at least three intermediate frequency subcarrier signals are frequency-multiplexed and transmitted, the at least three intermediate frequency subcarrier signals are frequency-converted into target frequency bands at transmission destination sides, and a signal bandwidth containing all the at least three intermediate frequency subcarrier signals is wider than a signal bandwidth of the target frequency bands,wherein when first and second pilot carriers are to be multiplexed and transmitted together with the at least three intermediate frequency subcarrier signals, frequencies of the at least three intermediate frequency subcarrier signals, a frequency of the first pilot carrier signal, and a frequency of the second pilot carrier signal are determined to obtain a frequency in the target frequency band by adding/subtracting an integral multiple of the frequency of the first pilot carrier signal and in an integral multiple of the frequency of the second pilot carrier signal to/from each of the frequencies of the at least the intermediate frequency subcarrier signals, wherein frequency subcarrier signals of at least three systems is an integral multiple of a predetermined frequency, and a frequency difference between the first pilot carrier signal and the second pilot carrier signal equals the predetermined frequency.
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Abstract
An optical communication system for optically transmitting transmission data from a transmitting station to a transmitting device includes an adder for adding an intermediate frequency subcarrier signal modulated with data to be transmitted to a pilot carrier signal as a sinusoidal wave, and an electro-optical converter for electro-optically converting the above sum signal to an optical signal by directly modulating a semiconductor laser element having a resonant frequency fr in accordance with the sum signal and transmitting the signal to an optical fiber for a down link. The frequency fIF of the intermediate frequency subcarrier signal and the frequency fLO of the pilot carrier signal satisfy
fLO−fIF≧1[GHz],
2×fIF<fLO<(⅔)×fr,
fIF<1[GHz], and
2 [GHz]<fLO.
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Citations
10 Claims
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1. A communication system in which at least three intermediate frequency subcarrier signals are frequency-multiplexed and transmitted, the at least three intermediate frequency subcarrier signals are frequency-converted into target frequency bands at transmission destination sides, and a signal bandwidth containing all the at least three intermediate frequency subcarrier signals is wider than a signal bandwidth of the target frequency bands,
wherein when first and second pilot carriers are to be multiplexed and transmitted together with the at least three intermediate frequency subcarrier signals, frequencies of the at least three intermediate frequency subcarrier signals, a frequency of the first pilot carrier signal, and a frequency of the second pilot carrier signal are determined to obtain a frequency in the target frequency band by adding/subtracting an integral multiple of the frequency of the first pilot carrier signal and in an integral multiple of the frequency of the second pilot carrier signal to/from each of the frequencies of the at least the intermediate frequency subcarrier signals, wherein frequency subcarrier signals of at least three systems is an integral multiple of a predetermined frequency, and a frequency difference between the first pilot carrier signal and the second pilot carrier signal equals the predetermined frequency.
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5. A communication system in which at least three intermediate frequency subcarrier transmission signals are frequency-multiplexed and transmitted from a transmitting/receiving station to one or a plurality of transmitting/receiving devices, the at least three intermediate frequency subcarrier transmission signals are frequency-converted into target frequency bands at the transmitting/receiving devices, at least three intermediate frequency subcarrier reception signals are frequency-converted in the transmitting/receiving devices, frequency-multiplexed, and transmitted to said transmitting/receiving station, and a signal bandwidth containing all the at least three intermediate frequency subcarrier transmission signals is wider than a signal bandwidth of the target frequency bands,
wherein when said transmitting/receiving station is to multiplex and transmit, to said transmitting/receiving device, first and second pilot carrier signals together with the at least three intermediate frequency subcarrier transmission signals, frequencies of the at least three intermediate frequency subcarrier transmission signals, a frequency of the first pilot carrier signal, and a frequency of the second pilot carrier signal are determined to obtain a frequency in the target frequency band by adding/subtracting an integral multiple of the frequency of the first pilot carrier signal and an integral multiple of the frequency of the second pilot carrier signal to/from each of the frequencies of the at least three intermediate frequency subcarrier transmission signals, and said transmitting/receiving device frequency-converts the intermediate frequency subcarrier reception signal using the integral multiple of the frequency of the first pilot carrier signal transmitted from said transmitting/receiving station and the integral multiple of the frequency of the second pilot carrier signal transmitted from said transmitting/receiving station.
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6. A communication system in which at least three intermediate frequency subcarrier transmission signals are frequency-multiplexed and transmitted from a transmitting/receiving station to one or a plurality of transmitting/receiving devices, the at least three intermediate frequency subcarrier transmission signals are frequency-converted into target frequency bands at the transmitting/receiving devices, at least three intermediate frequency subcarrier reception signals are frequency-converted in the transmitting/receiving devices, frequency-multiplexed, and transmitted to said transmitting/receiving station, and a signal bandwidth containing all the at least three intermediate frequency subcarrier transmission signals is wider than a signal bandwidth of the target frequency bands,
wherein when said transmitting/receiving station is to multiplex and transmit, to said transmitting/receiving device, first and second pilot carrier signals together with the at least three intermediate frequency subcarrier transmission signals, frequencies of the at least three intermediate frequency subcarrier transmission signals, a frequency of the first pilot carrier signal, and a frequency of the second pilot carrier signal are determined to obtain a frequency in the target frequency band by adding/subtracting an integral multiple of the frequency of the first pilot carrier signal and an integral multiple of the frequency of the second pilot carrier signal to/from each of the at least three frequencies of the intermediate frequency subcarrier transmission signs, and said transmitting/receiving device generates a local carrier signal using the integral multiple of the frequency of the first pilot carrier signal transmitted from said transmitting/receiving station and the integral multiple of the frequency of the second pilot carrier signal transmitted from said transmitting/receiving station, frequency-converts the intermediate frequency subcarrier transmission signal into the target frequency band using the local carrier signal, and frequency-converts a received radio frequency signal into the intermediate frequency subcarrier reception signal using the local carrier signal.
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7. A communication system in which at least three intermediate frequency subcarrier signals are frequency-multiplexed and transmitted, the at least three intermediate frequency subcarrier signals are frequency-converted into target frequency bands at transmission destination sides, and a signal bandwidth containing all the at least three intermediate frequency subcarrier signals is wider than a signal bandwidth of the target frequency bands,
wherein when first and second pilot carriers are to be multiplexed and transmitted together with the at least three intermediate frequency subcarrier signals, frequencies of the at least three intermediate frequency subcarrier signals, a frequency of the first pilot carrier signal, and a frequency of the second pilot carrier signal are determined to obtain a frequency in the target frequency band by adding/subtracting an integral multiple of the frequency of the first pilot carrier signal and in an integral multiple of the frequency of the second pilot carrier signal to/from each of the frequencies of the at least the intermediate frequency subcarrier signals, wherein a frequency interval between the intermediate frequency subcarrier signals of at least three systems is an integral multiple of a predetermined frequency, and a frequency of the second pilot carrier signal, equals the predetermined frequency.
Specification
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- Resources
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Current AssigneeKabushiki Kaisha Toshiba (Toshiba Corporation)
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Original AssigneeKabushiki Kaisha Toshiba (Toshiba Corporation)
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InventorsSeto, Ichiro, Tomioka, Tazuko, Ohshima, Shigeru
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Primary Examiner(s)Sedighian, M. R.
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Assistant Examiner(s)Payne, David C.
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Application NumberUS10/267,596Publication NumberTime in Patent Office1,132 DaysField of Search398/116, 398/31, 398/32, 398/182, 398/183, 398/186, 370/343, 370/481, 370/485, 370/491, 379/56.2, 359/124, 359/152US Class Current398/183CPC Class CodesH04B 10/504 using direct modulationH04J 14/0298 with sub-carrier multiplexi...H04J 3/1694 Allocation of channels in T...
