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本文提出了一种新的相干光纤通信中频稳定的方案——“二次外差锁相跟踪”。它使光外差中频稳定性比一般的频率负反馈方式提高了一个数量级,且光外差中频频率可自由调节。按此方案建立的实验系统,采用两个1.52μm He-Ne气体激光器分别作为独立的发射机和本机振荡器,在PZT控制电压为0~600V的范围内,实现了百兆赫量级的中频稳定,频率稳定性和频率复现性均达10~(-9)。二次外差方式有可能极大地提高光外差中频频率,为光波多路通信外差检测提供了一个易于实现的途径。 相似文献
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相干光通信的基础为相干调制以及外差检测技术。其中相干调制是采取传输信号对光载波的特征进行改变,那么在这个过程中就要保证光信号具备确定的频率以及相位,即存在相干光。在相干光系统应用过程中一般都会采用激光来作为相干光,由本机震荡产生的激光与信号光进行混频,从而得到具备规律变化的中频信号。本文对相干光通信系统当中的数字信号处理算法进行了分析并提出了相关的观点,供以参考。 相似文献
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介绍了自由空间光通信中的相干通信系统,通过对相干光通信中振幅键控(ASK),频移键控(FSK),相移键控(PSK),差分相移键控(DPSK)四种光载波相干调制方式性能的分析和比较,仿真结果得出PSK调制误码性能更好,提出了一种光载波外差差分相移键控(DPSK)系统. 相似文献
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光外差检测能提高无线激光通信系统的光电检测灵敏度,可以增大通信距离,并且能够采用多种调制方式。提出了一种基于副载波调制的无线光外差检测系统,重点对大气信道对外差系统的影响因素进行了分析。着重研究了偏振状态和波前修正联合控制、载波恢复、同态滤波等关键技术,以克服大气散射和大气湍流对外差检测系统的影响。最后介绍了无线光外差检测的实验系统,为无线激光通信外差检测技术提供理论依据和实验基础。 相似文献
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基于三频光外差法产生毫米波的研究 总被引:1,自引:1,他引:1
将三频光外差法运用到光纤无线系统(Radio-over-Fiber)中,研究了一种采用三频光外差法产生毫米波的RoF系统.在中心站产生三路不同波长的窄线宽光波,其中两路光波分别由光调制器调制上数据信号,另外一路作为本振光.经光纤传输后,再通过基站光探测器的探测混频产生两个不同频率的毫米波信号.结果表明,采用三束波长为1549.68nm、1549.52nm和1550nm的光波可产生两路分别携带10Gb/s下行基带数字信号的频率为40GHz和60GHz的毫米波,并实现基带信号在单模光纤中 20□的传输. 相似文献
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本文提出了一种新的基于副载波调制的无线光外差检测方案,用Optisystem对其进行仿真,计算了系统的外差增益,分析了影响无线光外差检测系统外差增益的几个主要因素,包括信号光的偏振态、激光器线宽、本振光功率及调制速率。从仿真结果可以得出:若信号光和本振光的偏振态不一致,会导致外差增益的下降;接收机灵敏度随光源激光器线宽的增大而降低,误码率要达到10-9,线宽最大不超过25KHz;增大本振光功率可以提高灵敏度,但这个提高不是无限地,存在一个最佳本振光功率,如果大于这个最佳值,信噪比反而会降低。 相似文献
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Lasers can be made to oscillate simultaneously at two frequencies by means of anisotropic or nonreciprocal resonator elements. A technique is described for stabilizing the resulting frequency separation by locking it to an external frequency source. The stabilized separation should be useful in optical heterodyne applications. 相似文献
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C. T. Elliott N. T. Gordon T. J. Phillips H. Steen A. M. White D. J. Wilson C. L. Jones C. D. Maxey N. E. Metcalfe 《Journal of Electronic Materials》1996,25(8):1146-1150
By taking advantage of Auger suppression techniques, the leakage currents of room temperature infrared detectors operating
in the LWIR band can be greatly reduced. At present, these detectors suffer from large 1/f noise and hence the improvement
in the detectivity resulting from the reduced leakage currents can only be realized at high frequencies. However, this is
not a problem for heterodyne systems which employ intermediate frequencies above 40 MHz. A thermo-electrically cooled Auger
suppressed infrared detector operated at 260K has been studied as a heterodyne detector. The device was operated with the
application of sufficient local oscillator power to double its dark current (about 0.3 mW) and a NEP of 2 x 10-19 W Hz−1 was deduced from heterodyne measurements. The frequency response is presently limited by a combination of the detector capacitance
and the series resistance to about 70 MHz and ways to reduce this series resistance are considered. 相似文献
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Watanabe S. Terahara T. Yokota I. Naito T. Chikama T. Kuwahara H. 《Lightwave Technology, Journal of》1993,11(1):116-127
Signal multiplexing techniques for coherent optical transmission are compared, and appropriate application for a coherent subcarrier multiplexing (SCM) system is discussed. Optical frequency modulation (FM) using direct modulation of a distributed-feedback laser diode (DFB-LD) and a heterodyne detection is shown to be feasible. A transmission system using a local laser in the transmitter is unaffected by polarization and is cost effective. Phase noise can be suppressed by a phase-noise-canceling circuit (PNC) in a heterodyne receiver. This circuit can also effectively compensate for the frequency of instability of light sources. A theoretical simulation of a coherent SCM system showed that 100 channels of 30-MHz FM signal or 15 channels of 155-Mb/s signal can be distributed to 10000 subscribers using single-stage or double-stage optical amplifiers 相似文献
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Glance B.S. Pollock K. Burrus C.A. Kasper B.L. Einstein G. Stulz L.W. 《Lightwave Technology, Journal of》1988,6(1):67-72
The results obtained with a fiber-optical star network using densely-spaced wavelength division multiplexing (WDM) and heterodyne detection techniques are reported. The system consists of three lasers transmitting at optical frequencies around 234000 GHz, spaced at a frequency interval of 300 MHz. The lasers are frequency-shift-key (FSK) modulated at 45 Mb/s. A 4×4 optical star coupler combines the three optical signals. The WDM signals received from one of the four outputs of the star coupler are demultiplexed by a heterodyne receiver. The minimum received optical power needed to obtain a bit-error rate of 10-9 is -61 dBm or 113 photon/bit, which is 4.5 dB from the shot noise limit. The degradation caused by co-channel interference was measured and found to be negligible when the channels, modulated at 45 Mb/s, are spaced by more than 130 MHz in the IF domain. These results indicate that a WDM coherent optical star network of this type has a potential throughput of 4500 Gb/s 相似文献
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Quadrature amplitude modulation (QAM) is an excellent modulation format for realizing optical communication systems with a high spectral efficiency of much greater than 1bit/s/Hz. We describe QAM coherent optical communication that we achieved by using heterodyne detection with a frequency-stabilized fiber laser and an optical phase-locked loop (OPLL) technique. The phase error variance of the intermediate frequency signal of the OPLL was 6.1times10-3 rad. A 1-Gsymbol/s 64-QAM coherent signal was successfully transmitted over 150km 相似文献
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Yamazaki S. Shibutani M. Shimosaka N. Murata S. Ono T. Kitamura M. Emura K. Shikada M. 《Lightwave Technology, Journal of》1990,8(3):396-405
A coherent optical frequency-division-multiplexing (FDM) experimental system for an optical CATV distribution service has been developed. This system employs a channel frequency spacing locked optical FDM transmitter and a random access optical heterodyne receiver. In the transmitter, ten 1.54-μm wavelength tunable distributed-Bragg-reflector laser-diode (DBR LD) modules were FSK modulated with a 400-Mb/s PN pattern. A reference pulse method is used for channel space control. Individual channel spacings for ten LDs are stabilized to 8 GHz. The random access optical heterodyne receiver is realized with a wavelength tunable local DBR LD, polarization diversity reception technique, and random access automatic frequency controller. A current address method realizes the random access function. The results of a ten-channel FDM transmission experiment carried out to evaluate these techniques are presented. It is estimated that over 80 channel high-definition TV signals can be distributed to 2000 subscribers with 500-GHz frequency tunable DBR LD. The feasibility of expanding the subscriber number to over 10000 was confirmed by an experiment with a traveling-wave optical amplifier 相似文献
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The effect of an external cavity semiconductor laser on the performance of a DPSK heterodyne optical system is evaluated. The actual shape of the frequency fluctuation spectral density of the optical source is taken into account, and a comparison with a PSK coherent heterodyne system is carried out 相似文献