The bias drift effect in the packaged LiNbO<sub>3</sub> modulator is investigated. The Bessel expansion of the dithered clock
shows that the harmonic component equal to the dither frequency can be synchronously demodulated to get the bias drift
and avoid the random phase difference between the clock or data and the dither signal. By using the time division control
method one control system can track two modulator bias drift in 40Gb/s RZ optical transmission system because the
optimum bias point changes very slowly.
Using broadband dispersion compensation CFBGs, over 500km-40Gbps NRZ transmission
system on G.652 fiber will be demonstrated without electric regenerator, FEC and Raman amplifier.
The power penalty is about 2dB @ BER =10<sup>-10</sup>.The CFBGs have better performance: 3dB band is
about 1.2nm, group delay ripple is less than 25ps near center wavelength, power ripple is less than 2dB,
and DGD is less than 1ps. In order to stabilize the DC bias of the LiNbO<sub>3</sub> MZ modulator, a
semiconductor cooler is applied to control the temperature. The effect is perfect.
In this paper we mainly discuss the low-cost way to improve the performances of wavelength routed optical networks. It
is really a tough work to reduce the probability of traffic loss due to the lack of abundant lightpath between arbitrary
nodes connected by precious wavelengths. Aiming to solve the problem, we probe an economical proposal that local
optical nodes can be equipped with extra receiving components with cheap Chirp Bragg Gratings. Under the
experimental platform of single-direction double-fibers optical network rings, this scheme has been verified, showing
the result that the traffic loss ratio can be reduced significantly by adding more Chirp Bragg Gratings especially under
heavy service loads. Consequently, it is feasible to improve the performance of all optical networks with several groups
of Chirp Bragg grating fibers with whole consideration of cost-effective optical network design.
A simple theoretical model is proposed for the study of timing jitter induced by intrachannel corss-phase modulation
(IXPM) in chirped fiber grating (CFG) compensating systems. The mechanism how CFG reduces the timing jitter is
studied in detail, theoretically and numerically. The reason why symmetrical power and dispersion scheme could
guarantee zero timing jitter is analyzed.
In this letter, aiming to obtain the best multicast performance of optical network in which the video conference
information is carried by specified wavelength, we extend the solutions of matrix games with the network coding theory
and devise a new method to solve the complex problems of multicast network switching. In addition, an experimental
optical network has been testified with best switching strategies by employing the novel numerical solution designed
with an effective way of genetic algorithm. The result shows that optimal solutions with genetic algorithm are
accordance with the ones with the traditional fictitious play method.
By using thin membrane plating technology in collimating lens, we successfully manufacture a 160Gbit/s time-division multiplexer basing on the combination of fiber and space structure method. The multiplexer is flexible according to your practical need, which can output 20, 40, 80, or 160Gbit/s signal. For 20, 40, 80 or 160Gbit/s multiplexer, insertion losses are 4dB, 6dB, 8dB and 16dB respectively. The low insertion loss provides maximum transmission power. It also has such features: polarization insensitivity, very short coherence length, high time-delay accuracy, and excellent temperature stability. An experiment of two degrees PMD compensation in 160Gbit/s RZ optical communication system is achieved. The PMD monitoring technique is based on DOP as error signal. A practical adaptive optimization algorithm was introduced in dynamic adaptive PMD compensation. The experimental results show the improvement in PMD. With this compensator, a significant improvement of system performance can be achieved by auto-correlative curves. The 2.5ps first-order and 15ps<sup>2</sup> second-order PMD are compensated. The PMD compensating time is less than 100ms.
The formulas for calculating nonlinear phase noise are proposed for both pre-compensation and post-compensation schemes. Based on these formulas, the phase noise, power tolerance and optimal signal peak power of both dispersion compensation schemes are analyzed and discussed in detail, respectively. The result shows that pre-compensation is more effective in reducing the nonlinear phase noise when compared with post-compensation. Its suppression ability improves with signal energy, ASE power spectral density and transmission distance increasing. The pre-compensation system possesses higher power tolerance than post-compensation system and the optimal signal power is increased when dispersion is taken into account, which results that the optimal phase shift is larger than 1rad. And the optimal signal power for pre-compensation system is larger than post-compensation system.
The dispersion of 8×10Gb/s wavelength division multiplex (WDM) system has been compensated by the cascaded chirped fiber Bragg gratings(CFBGs), with ITU-T standard wavelengths and wavelength grid. The ASE of the EDFA could be reduced, the OSNR of the transmitted signal could be increased and the fluctuation of the EDFA gain could be controlled in the certain scope by the dispersion compensated CFBGs' WDM system. Impact of cascaded CFBGs' delay ripple on dispersion compensation has been analyzed. Experiment of error-free 8×10Gb/s 2015km transmission without forward error correction (FEC) and electronic repeaters were demonstrated. In the transmission, simplex CFBGs compensators were used and no other form of dispersion compensators were adopted. The experiment result showed that the consistency of the dispersion compensating in each channel is perfect over 2015km optical fiber transmission. The experiment result does agree with the theoretic analysis.
The single-direction, self-healing all optical ring networks with double optical fibers based on the wavelength routing character of fiber gratings is introduced in this paper. The four-node network with ring topology can provide 16×10Gb/s optical transmission. The wavelength-selecting character of chirped fiber gratings is used for wavelength routing, and the function of dispersion compensation and multi-channel add/drop is achieved, too. The SNMP (Simple Network Management Protocol) model is referred to manage this network. Some important parameters are real-time observed to control the network. The results show that, if any optical fiber in the ring is broken down, the interrupted telecommunication service can be recovered automatically in less than 20ms.