Bidirectional WDM Transmission Research Articles

Optical self-injection mode-locking of semiconductor optical amplifier fiber ring with electro-absorption modulation—fundamentals and applications

The optical self-injection mode-locking of a semiconductor optical amplifier incorporated fiber ring laser (SOAFL) with spectrally sliced multi-channel carriers is demonstrated for applications. The synthesizer-free SOAFL pulse-train is delivered by optical injection mode-locking with a 10 GHz self-pulsed electro-absorption modulator (EAM). Such a coupled optical and electronic resonator architecture facilitates a self-feedback oscillation with a higher Q-factor and lower phase/intensity noises when compared with conventional approaches. The theoretical model of such an injection-mode-locking SOAFL is derived to improve the self-pulsating performance of the optical return-to-zero (RZ) carrier, thus providing optimized pulsewidth, pulse extinction ratio, effective Q-factor, frequency variation and timing jitter of 11.4 ps, 9.1 dB, 4 × 105, <50 kHz and 0.6 ps, respectively. Such a synthesizer-free pulsed carrier is also employed for the application in a 10 Gbit s−1 bi-directional WDM transmission network with down-stream RZ binary phase-shift keying (RZ-BPSK) and up-stream re-modulated RZ on–off-keying (RZ-OOK) formats. Under BPSK/OOK bi-directional data transmission, the self-pulsed harmonic mode-locking SOAFL simultaneously provides four to six WDM channels for down-stream RZ-BPSK and up-stream RZ-OOK formats with receiving sensitivities of −17 and −15.2 dBm at a bit error rate of 10−9, respectively.

Efficient path protection in bi-directional WDM systems

Bi-directional WDM transmission is a technique that allows data to be transmitted simultaneously in both directions of a fiber, with different sets of wavelength channels for each direction. Compared with unidirectional WDM systems, it not only saves the cost of deploying extra fibers, but also allows more flexible bandwidth provisioning. To exploit this flexibility, we investigate path protection schemes for bi-directional WDM transmission systems in this paper. With path protection, a call is accepted if and only if an active data path together with a disjointed backup path can be found in the network. With bi-directional WDM, backup resource sharing in both directions of a fiber is possible. Based on a set of judiciously designed link cost functions, two original path protection schemes are proposed in this paper, BiPro and BiProLP. BiProLP aims at further economizing the hardware cost incurred by BiPro. In contrast to the traditional unidirectional schemes, we show that both BiPro and BiProLP can yield noticeably lower call blocking probability, higher system capacity and shorter active/backup path length.

Bidirectional WDM transmission systems to enable using two identical sets of wavelengths over a single fibre

A new bidirectional WDM transmission technique using two identical sets of wavelengths for opposite directions on a single fibre is introduced. Its viability is suggested through a numerical analysis of power penalty owing to Rayleigh backscattering crosstalk.

Beat-frequency-locking기술을 이용한 12.5 GHz 채널간격 양방향 초고밀도 WDM 광채널 전송

Beat-frequency-locking기술을 이용한 12.5 GHz 채널간격 양방향 초고밀도 WDM 광채널 전송

Limitations imposed by Rayleigh backscattering in closely interleaved, bidirectional WDM transmission systems

By deriving signal-backscattering and backscattering-backscattering beat noises, this letter quantifies the performance impairment due to backscattering produced by closely spaced counterpropagating signals. Experiments using 10-Gb/s data signals verify the theoretical analysis. The interference between signal and backscattering induces significant impairment when their channel separation is less than the sum of the data rate and signal spectrum width. The spectral efficiency limitation imposed by backscattering is clarified for closely spaced, interleaved bidirectional transmission systems.

Ten-repeatered bi-directional WDM transmission of eight channels at 10 Gbit/s using single-wavelength-band-operating bi-directional amplifiers

Ten-repeatered, bi-directional WDM transmission of eight 10 Gbit/s channels (50 GHz spacing) over 550 km using single-wavelength-band-operating bi-directional amplifiers is successfully demonstrated. The bi-directional amplifier offers a backscattering-blocking function that eliminates any significant transmission performance degradation due to backscattering even with a cascade of ten repeaters.

Asymmetric bi-directional WDM transmission of 8 (total) 10 Gbit/s channels using bi-directional amplifier comprising single unidirectional optical amplifier and four-port Mach-Zehnder WDM coupler

The asymmetric bi-directional repeatered WDM transmission of eight (total) 10 Gbit/s. 5O GHz-spaced channels over three 50 km spans is demonstrated. A four-port Mach-Zehnder WDM coupler is used to construct a new hi-directional optical amplifier that operates in a single wavelength band. Directional asymmetry in channel-count and Rayleigh backscattering do not result in any significant performance degradation.

Multichannel bidirectional transmission using a WDM MUX/DMUX pair and unidirectional in-line amplifiers

We propose a repeated bidirectional WDM transmission system using cascaded WDM MUX/DMUX pairs as narrow-bandpass filters and reflection attenuators. Fiber span is increased by inserting unidirectional EDFAs between WDM MUX/DMUX pair as in-line amplifiers. A three-channel hybrid system with one 10-Gb/s and two 2.5-Gb/s channels is also demonstrated In the 1550-nm region for transmission over 150 km of dispersion-shifted fiber. Negligible power penalty due to back reflection was observed.

Stimulated raman effect in bi-directionally amplified and transmission WDM systems

One of the nonlinear effect-SRS effect in bi-directional WDM transmission systems is studied. Analytical and numerical results are given to show the effect of SRS. Systems with uni- and bi-directional EDFAs (Erbium doped fiber amplifiers) are also considered. A new method to deal with SRS effect in bi-directional svstems is drawn out.

Bidirectional 10-channel 2.5 Gbit/s WDM transmission over 250 km using 76 nm (1531–1607 nm) gain-band bidirectional erbium-doped fibre amplifiers

The widest, seamless, 76 nm (1531–1607 nm) 3 dB gain-band bidirectional amplifier is realised by combining an erbium-doped fluoride fibre amplifier (1531–1562 nm) and a gain-flattened erbium-doped silicate fibre amplifier (1562–1607 nm) in a novel configuration of gain-band separation between upstream and downstream signals. Bidirectional 10-channel WDM transmission at 2.5 Gbit/s over a 250 km conventional singlemode fibre is successfully demonstrated using our amplifiers as two bidirectional repeaters.

Bidirectional WDM Transmission with Spectrum Sliced LEDs

Experimentation d'une transmission bidirectionnelle sur 5 canaux a fibres optiques sur une longueur, depassant 8 km avec des fibres a gradient d'indice, un debit binaire de 167 Mbits/s par canal et une longueur d'onde aux alentours de 1,3 μm. Le recepteur est une photodiode avalanche InGaAs

1.3 μm/1.5 μm bidirectional WDM optical-fibre transmission system experiment at 144 Mbit/s

Results are reported of a 1.3 μm/1.5 μm bidirectional WDM transmission system experiment operating at 144 Mbit/s over 58 km of cabled single-mode fibre. Regenerators used Bell Laboratories-developed 1.3 and 1.5 μm InGaAsP semiconductor lasers, InGaAs PIN diodes, microwave monolithic amplifiers and optical bidirectional couplers.