Fiber optics transmission system
First Claim
1. A fiber optics transmission system which comprises:
- N radio access units each of which converts an up-link radio signal from a mobile radio, received by an antenna, into an up-link optical signal by means of a semiconductor laser device, converts a down-link optical signal intensity-modulated by a down-link radio signal into a down-link radio signal by means of a photodiode and transmits it to said mobile radio through said antenna, said N being an integer equal to or greater than 2;
up-link and down-link optical fiber lines to which said N radio access units are connected in cascade; and
a base unit which converts a down-link radio signal received from a control station into a down-link optical signal, provides it onto said down-link optical fiber line, converts an up-link optical signal received from said up-link optical fiber line into an up-link radio signal and transmits it to said control station; and
wherein;
said base unit comprises a noise detector for detecting beat noise, and a noise information generating section for generating noise information representing the presence of beat noise during its detection and for sending said noise information to said N radio access unit over said down-link optical fiber line; and
said radio access units each comprises a random signal generator for repeatedly generating a random value during the presence of said noise information, and a wavelength control circuit for controlling said semiconductor laser device to randomly select one of at least N wavelengths spaced a predetermined value or more apart in accordance with said random value.
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Accused Products
Abstract
In a fiber optics transmission system in which a plurality of access units are cascade-connected via up-link and down-link optical fiber lines and connected to a base unit, the base unit has a beat noise detector and a noise information generator and, upon detection of beat noise, noise information is sent to each access unit over the optical fiber lines. Each access unit has a random signal generator for generating a random value in response to the noise information and a wavelength control circuit for randomly selecting and controlling the oscillation wavelength of a laser diode, and each access unit repeats random wavelength selection until the noise information is reduced.
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Citations
11 Claims
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1. A fiber optics transmission system which comprises:
- N radio access units each of which converts an up-link radio signal from a mobile radio, received by an antenna, into an up-link optical signal by means of a semiconductor laser device, converts a down-link optical signal intensity-modulated by a down-link radio signal into a down-link radio signal by means of a photodiode and transmits it to said mobile radio through said antenna, said N being an integer equal to or greater than 2;
up-link and down-link optical fiber lines to which said N radio access units are connected in cascade; and
a base unit which converts a down-link radio signal received from a control station into a down-link optical signal, provides it onto said down-link optical fiber line, converts an up-link optical signal received from said up-link optical fiber line into an up-link radio signal and transmits it to said control station; and
wherein;said base unit comprises a noise detector for detecting beat noise, and a noise information generating section for generating noise information representing the presence of beat noise during its detection and for sending said noise information to said N radio access unit over said down-link optical fiber line; and said radio access units each comprises a random signal generator for repeatedly generating a random value during the presence of said noise information, and a wavelength control circuit for controlling said semiconductor laser device to randomly select one of at least N wavelengths spaced a predetermined value or more apart in accordance with said random value. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11)
- N radio access units each of which converts an up-link radio signal from a mobile radio, received by an antenna, into an up-link optical signal by means of a semiconductor laser device, converts a down-link optical signal intensity-modulated by a down-link radio signal into a down-link radio signal by means of a photodiode and transmits it to said mobile radio through said antenna, said N being an integer equal to or greater than 2;
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2. A fiber optics transmission system which comprises:
- N radio access units each of which converts an up-link radio signal from a mobile radio, received by an antenna, into an up-link optical signal, converts an intensity-modulated down-link optical signal into a down-link radio signal and transmits it to said mobile radio through said antenna, said N being an integer equal to or greater than 2;
up-link and down-link optical fiber lines to which said N radio access units are connected in cascade; and
a base unit which converts a down-link radio signal received from a control station into a down-link optical signal, provides it onto said down-link optical fiber line, converts an up-link optical signal on said up-link optical fiber line into an up-link radio signal and transmits it to said control station;said base unit comprising; a first photodiode for converting said up-link optical signal on said up-link optical fiber line into an up-link radio signal; noise detecting means for detecting the noise level in the output from said first photodiode and for determining if said noise level is higher than a predetermined level; noise information generating means for generating noise information indicating the presence of noise while said noise level is determined to be higher than said predetermined value; a first laser diode for emitting light to be provided onto said down-link optical fiber line; a first bias circuit for applying a bias current to said first laser diode; and a first combining circuit for intensity-modulating said bias current from said first bias circuit to said first laser diode by said down-link radio signal and said noise information from said noise information generating means and for applying said intensity-modulated bias current; and said each radio access unit comprising; a down-link optical coupler inserted in said down-link optical fiber line, for distributing a down-link optical signal; a second photodiode supplied with said down-link optical signal distributed from said down-link optical coupler, for converting it into a radio signal; an up-link optical coupler inserted in said up-link optical fiber line; a semiconductor laser device having a second laser diode optically coupled with said up-link optical coupler; an antenna for receiving an up-link radio signal from a mobile radio, or for transmitting a down-link radio signal from said second photodiode to said mobile radio; a noise information detector supplied with said radio signal from said second photodiode, for detecting said noise information in said radio signal; a random signal generator for generating, during the detection of said noise information by said noise information detector, at least N random values corresponding to at least N wavelengths of a predetermined spacing and for updating and holding said N random values with a predetermined period; a wavelength control circuit for controlling the oscillation wavelength of said second laser diode in accordance with said random value held in said random signal generator; a second bias circuit for applying a bias current to said second laser diode to oscillate it; and a second combining circuit for intensity-modulating said bias current from said second bias circuit by said up-link radio signal and for applying said intensity-modulated bias current to said second laser diode.
- N radio access units each of which converts an up-link radio signal from a mobile radio, received by an antenna, into an up-link optical signal, converts an intensity-modulated down-link optical signal into a down-link radio signal and transmits it to said mobile radio through said antenna, said N being an integer equal to or greater than 2;
Specification