论文部分内容阅读
已经研制成功的光缆——电缆信道互通电视电话传输系统,是由光信道机、话音转换控制器与改装的纵横制电话交换机构成,可同时进行图象、话音的转接,传输电视电话信息。电话拨号音、振铃、忙音等信号均能经光信道传输,经交换机与各信道互通。光信道机还可与没有电视电话端机的普通电话机通话。本文主要叙述光信道系统的研制简况。将调频的话音载频信号(2.0MHz)与基带视频信号(1MHz)复合放大后,对GaAlAS发光二极管(LED)进行直接强度调制,用阶跃型光缆作双工传输,接收端使用了低成本的Si-PIN光电二极管探测。接收机的灵敏度为-30.27dbm,未加权视频信噪比(Sp-p/Nrms)≥53db(调制度约50％),行时间非线性失真<2％,话音信噪比(Srms/Nrms)=42db,话音失真度小于1.5％(频偏7KHz)。使用1LED光源和3.5db/km损耗的阶跃型光纤,同时传输图象和话音,传输距离达3公里,话音清楚,直观图象清晰。
The optical cable-cable channel intercommunication television telephone transmission system that has been successfully developed is composed of an optical channel telephone, a voice conversion controller and a modified crossbar telephone exchange, which can simultaneously transfer images and voice and transmit the information of the television and telephone. Telephone dial tone, ringing, busy tone and other signals can be transmitted through the optical channel, the exchange with the channel interoperability. Optical channel machine can also be without a video phone terminal of the ordinary telephone conversation. This article describes the optical channel system development profile. After amplifying the FM voice carrier signal (2.0MHz) and the baseband video signal (1MHz), the GaAlAS LED is directly intensity modulated, and the step cable is used for duplex transmission. The receiving end uses the low cost Si-PIN photodiode detection. Receiver sensitivity is -30.27dbm, unweighted video signal-to-noise ratio (Sp-p / Nrms) ≥53db (modulation degree is about 50%), line time nonlinear distortion is less than 2%, voice signal to noise ratio (Srms / Nrms) = 42db, voice distortion is less than 1.5% (frequency deviation 7KHz). The use of 1LED light source and 3.5db / km loss of step-type fiber, while transmitting images and voice, transmission distance up to 3 km, clear voice, clear and intuitive images.