PWM_Communications

PWM_Communications - 102 JOURNAL OF LIGHTWAVE TECHNOLOGY,...

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102 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. LT-5, NO. 1, JANUARY 1987 Pulse Width Modulation for Analog Fiber-optic Communications s. Y Abstract-The pulse width modulation (PWM) technique has been revisited and analyzed to evaluate its merits for application analog signal transmission in fiber-optic links. Fourier analysis of the PWM reveals that it can he used as a vehicle launch an onto optical fiber when a symmetrical natural sampling process is used. The SNR of modulated depends on timing jitter of the carrier pulses wide-band (45 MHz) SNR of 45 dB ob- tained with commercially available multimode laser transmitter. A linear dynamic range of over 50 experimentally demon- strated. full bandwidth be utilized by using very high frequency, while a more popular frequency modu- lation provides about a 10-MHz 1 km of is conjunction a short wave- length (0.87 pm) LED Analog capability was demonstrated by constructing a simple video link using common laboratory equipment. performance of the sup- ports theory developed here elsewhere. experimental results indicated PWM is potentially‘very attractive for low-cost broad-band local area network (LAN) application, includ- ing future highly interactive offices, hospitals, automated factory floors. A I. INTRODUCTION LL DIGITAL pulse code modulation (PCM) meth- ods have been the preferred choice of fiber-optic transmission technology because of the inherent nonlin- earity of optical sources (notably for laser diode), which makes it difficult to use direct analog modulation tech- niques for fiber-optic communication systems. Moreover, digital systems offer considerable advantages over an an- alog transmission technique. For example, PCM allows the reproduction of the original signal at the repeater sta- tion without sacrificing its quality and the temporary stor- age of the data at any repeater station along the transmis- sion route. However, despite the current dominant trend toward all- digital transmission in the optical communications indus- tries, there may exist many potential applications where analog fiber-optic transmissions systems, compatible with existing analog transmission technology, are desirable [ 11. Examples include the transmission of multiplexed video signals [2]-[4], microwave radio [5], satellite terminals [6], sensory signals, and frequency division multiplexed voice channels [7]. Voice, image, and data transmissions are c,onverging, Manuscript received September 11, 1985; revised June 16, 1986. The author was with AT&T Bell Laboratories, Allentown, PA 18103. IEEE Log Number 8611042. He is now with Celanese Research Company, Summit, NJ 07901. SUH and the markets are emerging. The first, and perhaps the largest market, is the existing consumer base CATV with its pay-TV, request-TV, and special services subseg- ments. But the use of interactive video is emerging within large corporation complexes, universities , government sites, and military bases. Beyond these lie sectors such as the “back offices” of stock brokerages, banks, insurance companies, larger hospitals, and real estate offices. The
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This note was uploaded on 12/28/2011 for the course ECE 2C taught by Professor Yue during the Fall '08 term at UCSB.

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PWM_Communications - 102 JOURNAL OF LIGHTWAVE TECHNOLOGY,...

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