Bipolar optical FSK transmission experiments at 150 Mbit/s and 1Gbit/s

Bipolar direct modulation has been used to overcome the nonuniform low-frequency modulation response of distributed-feedback laser transmitter in optical FSK transmission experiments at 150 Mb/s and 1 Gb/s. The heterodyne receiver sensitivity was -48 dBm for 150 Mb/s and -39 dBm for Gb/s, independently of the pseudorandom pattern length. There was no degradation in receiver sensitivity with transmission through more than 100 km of fiber     

FSK heterodyne transmission experiments at 560 Mbit/s and 1 Gbit/s

Optical frequency-shift-keying (FSK) signals are obtained from directly modulated distributed feedback (DFB) semiconductor lasers. Experimental studies of the direct frequency modulation (FM) characteristics of the DFB lasers show a nonuniform FM response due to the competing effects of thermal modulation of the laser active region and carrier density modulation. Equalization of the signal current to the laser is employed to produce a flat FM response from 30 kHz to 1 GHz. Optical FSK transmission and heterodyne detection experiments at 560-Mbit/s and 1-Gbit/s are conducted at a wavelength of 1497 nm. Receiver sensitivities of -39 dBm at 560 Mbit/s and -37 dBm at 1 Gbit/s are obtained. Transmission through 100 km of single-mode fiber at 1 Gbit/s is achieved with no degradation in receiver sensitivity.     

Coherent lightwave transmission over 150 km fibre lengths at 400 Mbit/s and 1 Gbit/s data rates using phase modulation

We report coherent lightwave systems experiments over 150 km employing phase modulation at speeds of 400 Mbit/s and 1 Gbit/s. Bit error rates lower than 10?9 were attained with no evidence of an error rate floor. Receiver sensitivities of ?53.3 dBm and ?44.5 dBm (10?9 BER) achieved at 400 Mbit/s and 1 Gbit/s with a new balanced mixer receiver correspond to improvements of 10.7 dB and 7.5 dB over the best previously published direct detection results.     

140 Mbit/s optical FSK fibre heterodyne experiment at 1.54 ?m

An optical fibre heterodyne experiment using 2-FSK modulation at 140 Mbit/s has been operated in the 1.5 ?m loss window. A receiver sensitivity of ?55 dBm has been obtained; operation over a fibre link of 199.7 km showed no additional system degradation.     

140 Mbit/s and 560 Mbit/s FSK heterodyne polarisation diversity receiver using nearly perfect square law demodulators

A new frequency discriminator concept with nearly perfect square law demodulation characteristics is described. The performance of the device is verified in a 140 Mbit/s and 560 Mbit/s FSK heterodyne polarisation diversity transmission experiment.<>     

Wavelength-tunable 16 optical channel transmission experiment at 2Gbit/s and 600 Mbit/s for broadband subscriber distribution

Reports a 16 optical-channel single-mode fibre transmission experiment based on dense-WDM and tunable-etalon channel selection. Experiments at 2 Gbit/s and 600 Mbit/s over 10 km of single-mode fibre show little crosstalk penalty when the optical channel spacing is 2 nm. The system architecture is useful for high-capacity broadband subscriber distribution     

-70 dBm APD optical feedback receiver at 2.048 Mbit/s

Demonstrate an optical feedback (OFB) transimpedance receiver employing a GaInAs avalanche photodiode (APD) input device and an Si pin diode feedback element. The highest reported sensitivity of -70 dBm at 2.048 Mbit/s was achieved     

1 Gbit/s bipolar optical FSK transmission experiment over 121 km offibre

Bipolar direct modulation has been used to overcome the nonuniform low-frequency modulation response of a DFB laser transmitter in a 1 Gbit/s optical FSK transmission system. The heterodyne receiver sensitivity (nP¯) was -39 dBm for a 2²³-1 bit pseudorandom pattern, with no degradation in receiver sensitivity after transmission through 121 km of fibre     

1 Gbit/s optical FSK heterodyne transmission experiment over 100 km of single-mode fibre

A 1 Gbit/s optical FSK modulation/heterodyne detection transmission experiment has been conducted at a wavelength of 1497 nm. The receiver sensitivity is ?37dBm and no degradation is observed after transmission through 100 km of single-mode fibre.     

8 Gbit/s FSK modulation of DFB lasers with optical demodulation

Single-contact DFB lasers were frequency modulated by pseudorandom data at rates up to 8 Gbit/s by direct current modulation with no pre-equalisation of the modulation signal. The signals were optically demodulated by Fabry-Perot interferometers for conversion to ASK signals which were detected by a direct-detection receiver. At 8 Gbit/s the receiver sensitivity was -22 dBm.<>     

565 Mbit/s FSK direct detection system operating with four cascaded photoionic amplifiers

Reports experimental investigations at 565 Mbit/s of FSK transmission over a cascade of four laser amplifiers. Optical delay line demodulation was achieved using a fibre-based Mach-Zehnder interferometer. In practice the combination of this modulation format and demodulation technique could be used to minimise crosstalk effects for multichannel laser amplifier systems.<>     

Transmission experiments at 560 Mbit/s and 140 Mbit/s using single-mode fibre and 1300 nm LEDs

Transmission at 560 Mbit/s has been demonstrated using single-mode fibre and LEDs at 1300 nm. Surface-emitting, edge-emitting and super-radiant LEDs were used to transmit over maximum distances of 4.5 km, 15 km and 25 km, respectively. At 140 Mbit/s, the corresponding distances achieved with the same set of LEDs are 7.5, 35 and 50 km. respectively.     

40 Gbit/s electroabsorption modulated distributed feedback laser

A 40 Gbit/s multi-quantum well (MQW) electroabsorption modulator (EAM) with a lumped electrode monolithically integrated with a distributed feedback (DFB) laser is demonstrated. Superior characteristics are exhibited for the device, such as low threshold current of 18 mA, over 40 dB side-mode suppression ratio at 1 550 nm and more than 30 dB extinction ratio when coupled into a single-mode fiber. By adopting deep ridge waveguide and planar electrode structures combined with buried benzocyclobutene (BCB), the capacitance of the EAM is reduced down to 0.18 pF and over 33 GHz modulation bandwidth at a small signal has been demonstrated. Negative chirp operation is realized when the bias voltage is beyond 1.6 V.     

1.5 Gbit/s transmission system using FP laser as FSK discriminator/photodetector

An optical FM receiver based on a monoelectrode Fabry-Perot laser, with one antireflection coated facet is reported. The device, biased far above threshold, acts as an FSK discriminator/photodetector. An FSK transmission system, up to 1.5 Gbit/s with -30 dBm sensitivities for 10/sup -9/ BER, has been demonstrated using this laser. The speed is limited by the transmitter FM response and not by the receiver response.<>     

Polarisation-insensitive, 500 Mbit/s FSK transmission over 153 km by passive polarisation switching

Polarisation-insensitive heterodyne transmission of a 500 Mbit/s FSK signal over 153 km of fibre is realised by passive, data-induced polarisation switching. For the first time, this technique is used with a delay-line demodulator.<>     

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.     

Distance limits of 10 to 20 Gbit/s FSK transmission on standardfibre

A simple analysis is performed on an FSK transmission system using a high FM efficiency, high bandwidth DFB laser as a simple DFB transmitter and an FM/AM converter as an optical signal processor. It shows that optimum optical processing pushes the transmission limits to 150 km at 10 Gbit/s and to 40 km at 20 Gbit/s     

1.5 Gbit/s FSK transmission system using two-electrode Fabry-Perot buried heterostructure laser

The performance of a tunable two-electrode FP laser has been studied experimentally. An FSK transmission system up to 1.5 Gbit/s has been demonstrated using this laser. This new laser showed single longitudinal mode (20 dB side-mode suppression) lasing at different wavelengths through a range of 6.5 nm and minimum spectral linewidth of 30 MHz.<>     

Transmission experiments through 101 km and 84 km of single-mode fibre at 274 Mbit/s and 420 Mbit/s

Four transmission experiments through low-loss single-mode optical fibre at 1.3 ?m have been performed at 274 Mbit/s and 420 Mbit/s with different objectives. The first demonstrates transmission through 101 km of single-mode fibre at 274 Mbit/s with negligible dispersion penalty. The second experiment at 274 Mbit/s and 84 km uses only components suitable for use in an undersea cable system. Two additional experiments, both at 420 Mbit/s, accomplish a bitrate × distance product of 35 GHzkm with 84 km of fibre and show no dispersion penalty with 63 km and 2.4 ps/km nm dispersion.     

640 Mbit/s waveguide transmitter at 38 GHz

The principle of a digital waveguide transmitter working at 38 GHz is given. A pulse-code-modulation simulator, with a bit rate of 640 Mbit/s, produces the modulation signal and also allows error-rate measurements. Typical switching times of the modulator are less than 500 ps. These results have been obtained by use of a varactor diode installed in a rectangular R band waveguide.