G.C. Wilson

Predistortion of electroabsorption modulators for analog CATV systems at 1.55 /spl mu/m

A predistortion circuit with adjustable amounts of third- and fifth-order predistortion is studied both theoretically and experimentally. The circuit is used to cancel the third- and fifth-order intermodulation distortion of a 1.55-/spl mu/m integrated electroabsorption modulator/DFB laser. The CSO obtained is -61 dBc and the CTB is reduced 22.6 dB to -65 dBc. This performance is maintained after fiber amplification and propagation through 13 km of nondispersion shifted fiber due to the modulators low chirp. Dithering of the DFB lasers injection current is employed to increase the stimulated Brillouin scattering (SBS) threshold to +13.4 dBm.

Linearization of 1.55-/spl mu/m electroabsorption modulated laser by distortion emulation and reversal for 77-channel CATV transmission

An electroabsorption modulated laser (EML) is linearized by emulation and reversal of the nonlinear distortion using a companion EML inside an optoelectronic interferometer. Suppression of composite second-order and triple-beat signals to <-61 and <-63 dBc, respectively, have been achieved for a carrier-to-noise ratio (CNR) of 50 dB with a 77-channel loading of CATV carriers. Further performance enhancement can be expected through tailoring of device and component characteristics to suit the application.

Integrated electroabsorption modulator/DBR laser linearized by RF current modulation

We measure the two-tone intermodulation distortion of an electroabsorption modulator integrated with a DBR laser. Driving the modulator with an ac current yields a significant improvement in linearity over conventional voltage modulation at RF frequencies up to 10 MHz with more than 13 dBc reduction in the minimum distortion values at 0.5 MHz. High-frequency performance is presently limited by the capacitance loading the current drive.<<ETX>>

(FTTH) system providing broad-band data over cable modems along with analog and digital video

We demonstrate that by applying cable modem technology in a 1550-nm EDFA-based fiber-to-the-home (FTTH) system we can deliver broad-band data services along with analog and digital broadcast video. The data system shares 30-Mb/s downstream and 2.56-Mb/s upstream over 64 living units, while the broadcast video system provides 77 analog channels and /spl sim/1 Gb/s of digital video.

Long-haul DWDM/SCM transmission of 64- and 256-QAM using electroabsorption modulated laser transmitters

We report the first eight-wavelength hybrid dense wavelength-division multiplexing/subcarrier multiplexing (DWDM/SCM) transmission over 800 km (ten spans) of standard single-mode fiber, with 1.04-Gb/s payload on each wavelength in 35 6-MHz 64-quadrature amplitude modulated (QAM) channels, without dispersion compensation. Forward error-correction coding (FEC) was used to achieve error-free performance. Error-free performance on the majority of channels was also achieved for 64-QAM without FEC and for 256-QAM with FEC over 400 km. We used electroabsorption modulated laser transmitters.

Optimized predistortion of overmodulated Mach-Zehnder modulators with multicarrier input

Using a Mach-Zehnder modulator, predistorted to third-order only, 77-channel CTBs are measured that surpass published theoretical limits. New composite triple beat (CTB) limits for nth-order predistortion are calculated. Modulator and predistorter bandwidth limitations are shown by numerical simulation to limit the CTB obtainable in practical systems.

QAM-PON and super PON for access distribution networks

We propose a passive optical network (PON) system based on quadrature amplitude modulated (QAM) sub-carrier multiplexing (SCM) of 53 6 MHz 64/256-QAM channels. Sensitivities of -22 dBm and -17.5 dBm are achieved over 51 km of fiber under full duplex and broadcast delivery to 128 nodes for 64 and 256 QAM, respectively.

Suppression of SBS and MPI in analog systems with integrated electroabsorption modulator/DFB laser transmitters

In conclusion, we have demonstrated a simple means of suppressing SBS and multipath interference (MPI) when an electroabsorption modulated lasers (EML) is used as an optical transmitter for analog transmission at 1.55 /spl mu/m. This technique is essential to allow the high powers obtained with EDFAs to propagate with high CNR and low distortion.

Capacity limits imposed by intermodulation distortion on QAM SCM systems utilizing an optically linearized Mach-Zehnder modulator as transmitter

Summary form only given. Subcarrier multiplexed (SCM) systems at 1.55 /spl mu/m with a combination of amplitude modulation-vestigial sideband (AM-VSB) and QAM channels using a Mach-Zehnder (MZ) modulator have been demonstrated. Here, we calculate, for the first time to our knowledge, the ultimate limit that the intermodulation distortion (LMD) of an optically-linearized Mach-Zehnder externally-modulated laser imposes on the opacity of an all-optical AM system and determine the required received optical power.

Reduction of optical-beat interference (OBI) in cable-modem/FTTH systems using burst-mode lasers

We demonstrate an FTTH system providing broadcast analogue and digital video, plus interactive data, using cable modems. It operates without OBI impairment even for two interferers 8.5 dB stronger than the signal lasers. Burst-mode operation increases this margin.