4 Gbit/s pseudo-noise generator using GaAs MESFETs

A multiplexing gate using GaAs MESFETs is described and operation up to 4 Gbit/s is demonstrated. A 2 Gbit/s pseudo-noise generator which can deliver NRZ or RZ signals has been implemented with this circuit; the corresponding output sequences are shown.     

160 Gbit/s soliton data transmission over 200 km

Polarisation- and time-domain-multiplexed 160 Gbit/s soliton signals have been successfully transmitted over 200 km for the first time. The soliton source was a 10 GHz regeneratively modelocked fibre laser and a planar lightwave circuit was used for optical multiplexing. The soliton pulse width was ~1.5 ps. A polariser and a nonlinear loop mirror were used for demultiplexing from 160 to 10 Gbit/s     

Key technologies for terabit/second WDM systems with high spectralefficiency of over 1 bit/s/Hz

To fully utilize a limited gain bandwidth of about 35 nm (4.4 THz) in an erbium-doped fiber amplifier, an increase in signal spectral efficiency is required. In this paper, we investigate the key technologies to achieve terabit/second wavelength-division multiplexing (WDM) systems with over 1 bit/s/Hz spectral efficiency. Optical duobinary signals, which have narrower optical spectra than conventional intensity modulation signals, were applied to such dense WDM systems. The measured minimum channel spacing for 20-Gbit/s optical duobinary signals was 32 GHz and a spectral efficiency of over 0.6 bit/s/Hz was reached. By using polarization interleave multiplexing, spectral efficiency was expected to reach 1.2 bit/s/Hz in an ideal case with no polarization dependencies along the transmission lines. In such ultradense WDM systems with narrower channel spacing, stabilizing the wavelengths of laser diodes is an important issue for achieving stable operation over long periods. To do this, we developed a simple and flexible wavelength stabilization system which uses a multiwavelength meter. The wavelengths for 116 channels with 35-GHz spacing were stabilized within ±150 MHz. The stabilization system is applicable to ultradense WDM signals with a spectral efficiency of over 1 bit/s/Hz by employing wavelength interleave multiplexing and an optical selector switch. On the basis of these investigations, we demonstrated a 2.6-Tbit/s (20 Gbit/s×132 channels) WDM transmission by using optical duobinary signals. In addition, 1.28-Tbit/s (20 Gbit/s×64 channels) WDM transmission with a high spectral efficiency of 1 bit/s/Hz was achieved by using polarization interleave multiplexing     

Multi/demultiplexing in Gbit/s range using dual gate GaAs m.e.s.f.e.t.s

Multiplexing from 1 to 2 Gbit/s and corresponding demultiplexing from 2 to 1 Gbit/s including clock regeneration and pulse width reduction has been performed using dual gate GaAs m.e.s.f.e.t.s. Circuits and time behaviour of input, clock and output signals are shown.     

A versatile ECL multiplexer IC for the Gbit/s range

A new approach to digital multiplexing for communication systems operating in the Gbit/s range is presented. With a single function, monolithically integrated in the established silicon bipolar process, many operations required by the communication system's multiplex equipment are achieved at data rates of up to 3 Gbits/s. The IC is a four-channel multiplexer designed to interface readily with ECL families. Demonstrations of the ICs performance include pseudorandom pattern generation by multiplexing ECL inputs up to 2 Gbits/s, demultiplexing into ECL registers at 1 Gbits/s, clock extraction in a 560 Mbit/s coaxial cable transmission system, and a modulo-n divider technique for timing generation using ECL feedback shift registers for frequencies up to 1.6 GHz. The demonstrations highlight the multiplexer's ability to effectively extend the system speed limit of commercially available ECL from a few hundred Mbits/s to the Gbit/s range. An eight-input multiplexer using three chips in a hybrid assembly is demonstrated multiplexing a static input pattern up to 2.8 Gbits/s.     

Applications of single and dual gate GaAs MESFETs for Gbit/s optical data transfer systems

Intrinsic large signal rise and fall times of less than 30 ps without charge storage demonstrate the potential of single and dual gate GaAs MESFETs for Gbit/s optical communication systems. The applications as signal regenerator, bit synchronizer, laser modulator, multiplexer, and demultiplexer are shown. Using only one dual gate GaAs MESFET clock and pulse shape regeneration as well as 1 Gbit/s laser modulation is performed. Bit synchronization is demonstrated up to 4 Gbit/s. 1 to 2 Gbit/s and 2 to 4 Gbit/s multiplexing as well as 2 to 1 Gbit/s demultiplexing with additional clock and pulse shape regeneration is shown using dual gate FETs. 2 to 4 Gbit/s multiplexing without clock regeneration is also accomplished using single gate GaAs MESFETs.     

80 Gbit/s soliton data transmission over 500 km with unequalamplitude solitons for timing clock extraction

Single-polarisation 80 Gbit/s soliton data signals have been successfully transmitted over 500 km. The soliton source was a modelocked fibre laser and a planar lightwave circuit was used for stable optical multiplexing. A nonlinear loop mirror was used for demultiplexing, in which unequal amplitude solitons were used for clock extraction     

Differential precoder IC modules for 20-and 40-Gbit/s opticalduobinary transmission systems

This paper reports on 20- and 40-Gbit/s differential precoder modules for optical duobinary transmission systems. These precoder modules overcome the speed limit of a conventional precoder by parallel processing. The proposed precoders handle two or four parallel signals before multiplexing with data rates of one-half or one-quarter the transmission bit rate, and the final preceded signal is obtained by multiplexing the precoder output bit by bit, production-level 0.2-μm gate-length GaAs MESFET's were used to fabricate the precoders. The precoders are mounted in an RF package. They successfully performed 20- and 40-Gbit/s precoding for the first time, and the 20-Gbit/s precoder achieved a maximum precoding rate of 22 Gbit/s, which is 76% faster than that of the conventional circuit using the same MESFETs. The 40-Gbit/s precoder performs 40-Gbit/s precoding when combined with a 40-Gbit/s multiplexer unit. Twenty-Gbit/s optical duobinary transmitter and receiver circuits using the 20-Gbit/s precoder module successfully generate fully encoded optical duobinary signal at this rate for the first time. These circuits show a receiver sensitivity of -28.6 dBm for a bit error rate of 1×10^-9     

Feasibility of a 1 Gbit/s/ 565 Mbit/s bidirectional single-mode-fibre subscriber line for B-ISDN using 1279 nm/ 1315 nm wavelength division multiplexing

A laboratory system, transmitting 1 Gbit/s signals to a subscriber station and 565 Mbit/s signals back to a head station via one 20 km-long single-mode fibre, has been realised. Wavelength division multiplexing via two 3 dB fibre couplers of selectivity ?0.04 dB/nm has been used. The experiment demonstrates that bidirectional single-mode-fibre transmission is applicable to a future B-ISDN subscriber network.     

High-sensitivity and wide-dynamic-range 10 Gbit/s APD/preamplifieroptical receiver module

InAlAs avalanche photodiodes (APD) and SiGe-HBT preamplifier 10 Gbit/s optical receiver modules have been developed. The measured back-to-back minimum sensitivity and the optical overload with a pseudorandom binary sequence of 2³¹ - 1 at a bit error rate of 10^-9 are -29.5 and +0.4 dBm, respectively. The dynamic range is 29.9 dB. These results show the highest sensitivity and the widest dynamic range yet reported for 10 Gbit/s APD receivers     

Broadband CPN demonstrator using wavelength and time divisionmultiplexing

RACE Project 1036 is developing the technology for a broadband customer premises network (CPN) using wavelength and time division multiplexing (WTDM). Features include close wavelength spacing (4 nm in the 1500 nm band), high-speed time multiplexing (2.5 Gbit/s, STM-16), and a layered control protocol. An initial demonstrator with two wavelengths carrying TV signals at 155 Mbit/s was exhibited in the autumn of 1990 and is now evolving into the final demonstrator due at the end of 1992 which will show 16 wavelengths and a 2.5 Gbit/s multiplex of HDTV, TV, and sound. The authors describe the devices made in the Project, the demonstrators, and the performance results achieved so far     

10 Gbit/s, 1200 km error-free soliton data transmission using erbium-doped fibre amplifiers

Soliton data signals at 10 Gbit/s have been successfully transmitted for the first time through a 1200 km dispersion-shifted fibre by using 24 erbium-doped fibre amplifiers. A bit error rate below 10/sup -13/ was obtained with 2/sup 20/-1 pseudorandom patterns.<>     

Over 80 Gbit/s 2:1 multiplexer and low power selector ICs using InP/InGaAs DHBTs

A 2:1 multiplexer (MUX) and low power selector ICs have been successfully designed and manufactured using an InP/InGaAs DHBT technology. The 2:1 MUX has been tested at data rates up to 80 Gbit/s with an output swing of 600 mV, while the selector IC has achieved operation speed up to 90 Gbit/s at a power consumption of only 385 mW.     

High-speed optical pulse transmission at 1.29-µm wavelength using low-loss single-mode fibers

Optical-fiber transmission experiments in the 1.3-μm wavelength region are reported. GaInAsP/InP double-heterostructure semiconductor laser emitting at 1.293 μm is modulated directly in nonreturn-to-zero (NRZ) codes at digit rates tanging from 100 Mbit/s to 1.2 Gbit/s. Its output is transmitted through low-loss GeO2-doped single-mode silica fibers in 11-km lengths. Transmitted optical signals are detected by a high-speed Ge avalanche photodiode. Overall loss of the 11-km optical fibers, including 11 splices, is 15.5 dB at 1.3 μm. Average received optical power levels necessary for 10^-9error rate are -39.9 dBm at 100 Mbit/s and -29.1 dBm at 1.2 Gbit/s. In the present system configuration, the repeater spacing is limited by loss rather than dispersion. It seems feasible that a more than 30 km repeater spacing at 100 Mbit/s and a more than 20 km even at 1.2 Gbit/s can be realized with low-loss silica fiber cables, whose loss is less than 1 dB/km. Distinctive features and problems associated with this experimental system and constituent devices are discussed.     

All-optical time division multiplexing using four-wave mixing

A new approach to all-optical time-division multiplexing is proposed and experimentally demonstrated. A 100 GHz 1.547 μm signal is modified by time-delayed 6.3 Gbit/s signals to generate subchannels in a 1.557 μm 100 Gbit/s signal via four-wave mixing     

Narrow-linewidth strained-layer 1.5 mu m multiquantum well distributed feedback lasers

The performance characteristics of narrow-linewidth strained-layer 1.5 mu m multi-quantum-well distributed feedback (MQW-DFB) lasers are presented. Measured linewidth as low as 3.5 MHz has been observed for one of the 250 mu m long devices at 14.4 mW output. Under 1.7 Gbit/s 1.0, 1.0, . . . pattern signal modulation, the lasers have 20 dB down full width chirp in the range of 5-6 AA for the off state at 0.8 I/sub th/. The chirp widths are about half of those of bulk-active DFB lasers. A 1.7 Gbit/s amplitude-shift-keying transmission experiment using one of the low-chirp lasers has been demonstrated. The transmission over 60 km of standard fibre only result in a 0.8 dB dispersion power penalty and has a receiver sensitivity of -36.2 dBm at BER=10/sup -9/.<>     

2×10 Gbit/s WDM 1310-nm optical transmission over 63.5-kmstandard single-mode fiber using optical preamplifiers

Twenty Gbit/s transmission over 63.5 km SMF at 1310 nm is reported by using two channel 10 Gbit/s wavelength (de)multiplexing (Δλ=1.5 nm). Two 1310 nm SL-MQW semiconductor optical amplifiers are utilized for loss compensation and sensitivity improvement. For the 1310 nm wavelength domain, a record bitrate x distance product of 1.27 Tbit/s.km has been obtained. Crosstalk penalties are identified, and the feasibility of an extension up to at least four, 10 Gbit/s channels is discussed     

20 Gbit/s optical time multiplexing with TJS GaAlAs lasers

Optical time multiplexing has been demonstrated using ultrashort optical pulses (30 ps) generated by direct modulation of TJS GaAlAs lasers. With the detection method used, an intensity correlator using second-harmonic generation in LiIO3, a bit rate of 20 Gbit/s was observed. However, the ultrashort optical pulses generated by the TJS lasers indicate that optical time multiplexing at 30 Gbit/s can be achieved.     

Wired and single sideband wireless service based on a single optical modulator

In order to provide more flexible and convenient service for users in the hybrid transmission network,a novel system using a single optical modulator to provide wired and single side band (SSB) wireless signal was proposed.By combining the application of dual-polarization binary phase shift keying modulator (DP-BPSK),phase shifter and other devices,wired and SSB wireless signals were directly generated to suppress the walk-off effect caused by dispersion,and the effective transmission of 5 Gbit/s SSB wireless signal carried on 40 GHz millimeter wave and 10 Gbit/s wired signal over 65 km single-mode fiber (SMF) were successfully achieved.The experiments show that the application of polarization multiplexing technology and optical subcarrier multiplexing technology can make the signal have a greater improvement in transmission rate and performance,and play an important role in the future broadband communication network.     

Study of dual-polarization OQAM-OFDM PON with direct detection

An offset quadrature amplitude modulation orthogonal frequency-division multiplexing (OQAM-OFDM) passive optical network (PON) architecture with direct detection is brought up to increase the transmission range and improve the system performance. In optical line terminal (OLT), OQAM-OFDM signals at 40 Gbit/s are transmitted as downstream. At each optical network unit (ONU), the optical OQAM-OFDM signal is demodulated with direct detection. The results show that the transmission distance can exceed 20 km with negligible penalty under the experimental conditions.