Bryon L. Kasper

4 Gbit/s PSK Homodyne Transmission System Using Phase-Locked Semiconductor Lasers

Homodyne detection of 1 Gb/s pilot-carrier (BPSK) optical signals using phase-locked 1.5 mu m external-cavity semiconductor lasers is discussed. After 209 km fiber transmission of a 2/sup 15/-1 pseudorandom binary sequence (PRBS), the measured receiver sensitivity is 52.2 dBm or 46 photons/bit. Experimental evidence of the data-to-phase-lock crosstalk that potentially limits the usable ratio of linewidth to bit rate in pilot-carrier PSK homodyne systems is presented.<<ETX>>

High Bit-Rate Receivers, Transmitters, and Electronics

Publisher Summary This chapter reviews the design of practical high bitrate receivers, transmitters, and electronic circuits. It illustrates the performance of various detectors, analyzes receiver sensitivity, and considers system impairments. The chapter also explores directly and externally modulated transmitters and modulation formats namely Return-to-Zero (RZ) and Chirped RZ (CRZ). The electronic circuit elements found in the transmitters and receivers— including broadband amplifiers, clock and data recovery circuits, and multiplexers—are also presented. The advent of optical amplifiers particularly, Erbium–Doped Fiber Amplifiers (EDFAs), have revolutionized lightwave systems by making Dense–Wavelength Division Multiplexing (DWDM) the cheapest long-haul transmission technology. Optical preamplifiers using EDFAs exhibit very high receiver sensitivity and are employed extensively in the WDM applications. It is noted that by taking advantage of the high processing speed and large–scale integration of advanced semiconductor IC technologies, many optical fiber transmission impairments at high data rates can be mitigated by low–cost high–performance electronics such as advanced electronic equalizers and spectrally efficient coders and decoders. Thus, high–speed electronics can become a critical enabler to move the capacity of ETDM/WDM optic fiber communication systems to petabits per second with individual channels running at 100 Gbit/s in future.

10 Gb/s transmission over 3.3 km using an uncooled InAlGaAs Fabry-Perot laser operating up to 85/spl deg/C

Here we report on transmission with an uncooled directly-modulated Fabry-Perot InAlGaAs multi-quantum-well laser at 1310 nm over 11 ps/nm dispersion and operating at temperatures from 0 C to 85 C with transmission penalty less than 1 dB. This would allow transmission over 3 km of single-mode fiber.

High speed, high performance laser module

We will present the performance data and discuss a few pertinent design details of a cooled directly modulated laser (DML) module that is targeted for use in several SONET OC-192 applications and capable of addressing 10G Ethernet requirements. The intent of the presentation is to demonstrate the performance potential of the module operating at 1310 nm wavelength for these applications. The four primary technical areas of focus are: (1) the ability to continuously operate in adverse environmental conditions, i.e. 85/spl deg/C case temperature, (2) demonstrate transmission up to 80 km is achievable via use of, (3) a high efficiency optical coupling design, and (4) ease of RF interface due to low RF return loss and high bandwidth. These all assume that the lasers intrinsic design is properly specified and well matched to the package design. The regime of engineering design is approaching the practical limits and diminishing returns in terms of RF and optical coupling efficiencies. This suggests that further substantial improvements require a change in the underlying technology.

Coherent Lightwave Transmission at 2 Gb/s Over 170 km of Optical Fiber Using Phase Modulation

The use of coherent techniques in lightwave communications can provide improved sensitivities over those that have been obtained using direct detection receivers[l]. For this reason coherent techniques may be useful for long-haul, high-bit-rate systems. We have explored this possibility in a system operating at 2 Gb/s, and achieved 170 km transmission. This represents a record bit rate, as well as bit-rate-distance product (340 Gb km/s), for a coherent lightwave system. It is also a record distance for any system operating at 2 Gb/s.

Balanced dual-detector receiver for optical heterodyne communication at Gbit/s speeds

Balanced-mixer receivers for optical systems, first proposed by Oliver,1 have been shown to be useful in suppressing local oscillator (LO) excess intensty noise.2 Furthermore, such a receiver requires less local oscillator power than does a conventional single-detector receiver. This latter advantage is particularly important for high-bit-rate optical heterodyne systems, since receiver thermal noise increases rapidly in typical PINFET front ends as the intermediate frequency is increased. Hence, to ensure that LO shot noise dominates thermal noise (as desired for maximum sensitivity), LO power must be increased at high speeds. With the limited ouput power available from present semiconductor lasers, sufficient LO power is difficult to obtain for speeds of Gbit/s and Intermediate frequenices near 2 GHz.

Information-Bandwidth-Limited Transmission at 8Gb/s Over 68.3km of Optical Fiber

Although the fundamental and practical limits of characteristics such as laser power, transmitter/receiver speed, transmitter spectral purity, receiver sensitivity, fiber dispersion, and fiber loss can be probed at the device level, the efficiency with which a given component trades off one characteristic against another is best evaluated in the system environment. One figure of merit that measures the degree of optimization is the bit-rate times distance product. Another is the spectral width used by the transmitter, since this determines the ultimate capacity of the fiber.

Ruggedized photonic components for avionics and vehicle applications (invited)

Commercial-off-the-shelf photonic components designed for datacenter or industrial applications do not typically satisfy the environmental ruggedness requirements of aerospace and military applications. In order to reduce costs and schedule risk for insertion of photonic components into these harsh-environment avionic and vehicle applications, we developed a variety of rugged photonic transceivers and media converter modules. We then performed qualification testing to demonstrate that these modules meet or exceed the requirements.