摘要:
An object of the present invention is to realize almost the same transmission characteristic in all wavelengths at a transmission rate of 10 Gb/s or more. An optical transmitter 10 outputs WDM signal light multiplexed with signal light of a plurality of wavelengths toward an optical transmission line 12. The optical transmission line 12 comprises an optical transmission fiber 14, an optical repeating amplifier 16 and a dispersion compensating fiber 18. The gain characteristic of the optical repeating amplifier 16 is set so that the gain becomes the maximum at the effective zero dispersion wavelength of the optical transmission line 12 and that lowers inversely proportional to the distance from the effective zero dispersion wavelength. The whole optical transmission line 12 is set so that the peak power deviation between the effective zero dispersion wavelength &lgr;0 and the wavelength &lgr;1 or &lgr;n on both end becomes approximately 4 dB.
摘要:
An optical communication system of a construction wherein the average wavelength dispersion value of the transmission optical fiber used, the optical output intensity of each optical amplifier repeater inserted in the transmission optical fiber and the widths of return-to-zero optical pulses transmitted over the transmission line are determined so as to compensate for the pulse compression effect by the nonlinear optical effect produced on the optical pulses by the pulse spreading effect by the wavelength dispersion effect. An optical multiplexer in the optical transmitting device time-division multiplexes the return-to-zero optical pulses, and the optical multiplexed signal is provided as an alternating-amplitude optical signal with the amplitudes of the return-to-zero optical pulses alternated.
摘要:
The present invention provides a wavelength division multiplexed optical fiber transmission equipment which can increase the number of channels of the WDM signal by reducing a required bandwidth of optical signals while suppressing an interference between signals caused by four-wave mixing. A WDM optical transmitting terminal comprises five or more optical transmitters and the wavelengths of optical signals from the optical transmitters are set such that the spacing between the wavelengths of two signals is re-used as the spacing between the wavelengths of other two signals separated by the above signals by two or more waves and there is no periodicity in the channel spacing s. For instance, the wavelengths of the optical signals are set as shown in FIG. 1. As the result, deterioration in the transmission characteristics of the optical signals can be effectively reduced and, at the same time, the maximum number of channels of the WDM signal can be increased. To the WDM optical transmitting terminal is added polarization state controllers for controlling the state of polarization such that the states of polarizations of adjacent signals cross each other at an output of the WDM optical transmitting terminal.
摘要:
It is the object of the present invention to optimize the degradation due to the four-wave mixing of wavelength multiplexed signals and the distortion due to the chromatic dispersion, thereby to provide a wavelength division multiplexed optical fiber transmission equipment having good transmission characteristics. A WDM transmitting terminal consists of four transmitters of channels 1 to 4, and a wavelength-division multiplexer. Further, a WDM receiving terminal consists of an equalization optical fiber, a wavelength-division demultiplexer, and four receivers of the channels 1 to 4. The WDM transmitting terminal and the WDM receiving terminal are interconnected by transmission optical fibers and an optical amplifier. The equipment is designed so that the wavelengths .lambda..sub.1, .lambda..sub.2, .lambda..sub.3 and .lambda..sub.4 of the optical signals output from the transmitters all lie on the short-wavelength side with respect to the average zero-dispersion wavelength .lambda..sub.0. This allows the distortion due to the four-wave mixing of a wavelength multiplexed signal to be reduced. The equalization optical fiber has a chromatic dispersion of a sign opposite to the chromatic dispersion of the optical fibers forming a transmitting path, thereby for compensating the chromatic dispersion of the optical signals output from the transmitters.
摘要:
An equalizing apparatus for equalizing gains of wideband wavelength-division multiplexed light and for improving the S/N ratio comprises a plurality of optical amplifyer for optically amplifying light in different wavelength groups, respectively; and multiplexer for multiplexing optically amplified light from said plurality of optically amplifying means.
摘要:
Detection of an optical pulse position uses an optical pulse string with a determined repetitive ratio and an electric clock signal with a same frequency as the repetitive ratio of the optical pulse string. A phase of the electric clock signal oscillator is shifted and supplied to an optical modulator. The optical modulator modulates the optical pulse string based on the electric clock signal and outputs a modulated optical signal. A photo detector converts the modulated optical signal output from the optical modulator to an electric signal. The phase shift amount of the electric clock signal is controlled to maximize an output from the photo detector. Additionally, a dither signal may be used in the control of the phase shift, more than the optical modulator may be employed, and/or more than color light source may be employed. The use of at least one of feed forward and feedback control provided by maximizing an output of the photo detector allows an optical pulse having a short width to be realized.
摘要:
An optical transmitter which reverses the ON-OFF state of the optical intensity of a bright soliton lightwave and generates a dark soliton lightwave having an optical phase shift, an optical receiver for the dark soliton lightwave, and a superfast, high-capacity optical transmission system which is capable of increasing the soliton pulse array density while suppressing timing jitter. The optical transmission system is provided with the optical transmitter which transmits a dark soliton lightwave having digital information, the optical receiver which receives the dark soliton lightwave as a return-to-zero pulse and a transmission optical fiber interconnecting the transmitter and the receiver. The system has a construction in which the transmission optical fiber has, at the wavelength of the transmission lightwave, a normal dispersion value which makes negative the average wavelength dispersion value over the entire length of the optical fiber, and the average value of the wavelength dispersion value and the optical output intensity of the transmission optical fiber have values so that a non-linear optical effect and a wavelength dispersion effect, which are exerted on the transmission lightwave, are balanced with each other.
摘要:
An optical amplifying-repeating transmission system is disclosed which is composed of an optical fiber for transmitting a lightwave signal with digital information added to return-to-zero lightwave pulses and a plurality of optical amplifying repeaters inserted in the optical fiber for transmission use. The mean value of wavelengths at which the wavelength dispersion of the optical fiber is zero is smaller than the wavelength of the lightwave signal which is transmitted over the system. The accumulated wavelength dispersion value of the optical fiber tends to increase with the distance of transmission, from a macroscopic viewpoint. The optical fiber for transmission is divided into a plurality of sections. In accordance with the accumulated wavelength dispersion value of the optical fiber in each section except at least the last one, a wavelength dispersion medium, which locally changes the wavelength dispersion in a manner to cancel the accumulated wavelength dispersion in the section at the wavelength of the lightwave signal, is inserted in the section to eliminate the accumulation of the timing jitter.
摘要:
Detection of an optical pulse position uses an optical pulse string with a determined repetitive ratio and an electric clock signal with a same frequency as the repetitive ratio of the optical pulse string. A phase of the electric clock signal oscillator is shifted and supplied to an optical modulator. The optical modulator modulates the optical pulse string based on the electric clock signal and outputs a modulated optical signal. A photo detector converts the modulated optical signal output from the optical modulator to an electric signal. The phase shift amount of the electric clock signal is controlled to maximize an output from the photo detector. Additionally, a dither signal may be used in the control of the phase shift, more than the optical modulator may be employed, and/or more than color light source may be employed. The use of at least one of feed forward and feedback control provided by maximizing an output of the photo detector allows an optical pulse having a short width to be realized.
摘要:
An optical transmitter which reverses the ON-OFF state of the optical intensity of a bright soliton lightwave and generates a dark soliton lightwave having an optical phase shift, an optical receiver for the dark soliton lightwave, and a superfast, high-capacity optical transmission system which is capable of increasing the soliton pulse array density while suppressing timing jitter. The optical transmission system is provided with the optical transmitter which transmits a dark soliton lightwave having digital information, the optical receiver which receives the dark soliton lightwave as a return-to-zero pulse and a transmission optical fiber interconnecting the transmitter and the receiver. The system has a construction in which the transmission optical fiber has, at the wavelength of the transmission lightwave, a normal dispersion value which makes negative the average wavelength dispersion value over the entire length of the optical fiber, and the average value of the wavelength dispersion value and the optical output intensity of the transmission optical fiber have values so that a non-linear optical effect and a wavelength dispersion effect, which are exerted on the transmission lightwave, are balanced with each other.