Temporal-Spectral Imaging of optical pulses constitutes a technique for the measurement of
fast optical spectral. The experiment to perform real-time spectral analysis of optical pulses in fibre by
time lens is demonstrated in this article. The use of time lens in the demodulation of the grating
wavelengths is discussed in this article.
The bias drift effect in the packaged LiNbO3 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 =10-10.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 LiNbO3 MZ modulator, a
semiconductor cooler is applied to control the temperature. The effect is perfect.
This paper proposes a single source SBS slow light scheme. This approach splits the incoming pulse train into two beams. One of the beam is used as the "probe"; the other beam is modulated at a frequency which is close to or identical to the half Brillouin shift, and can be used as multiple "pump". The quantitative model shown that the delay and slow light bandwidth can be controlled by the modulation amplitude and the maximum bandwidth is approximately two times of Brillouin shift by choosing an optimum value of the modulation amplitude.
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.
KEYWORDS: Polarization, Multiplexers, Feedback signals, Wave plates, Signal attenuation, Telecommunications, Digital signal processing, Optical communications, Optical amplifiers, Control systems
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 15ps2 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.
A modified carrier suppressed return-to-zero (CSRZ) format was forward in this paper, and it helps to improve the extinct ration (ER) and signal-to-noise ration (SNR) of the transmitted signal. Experiment of 2560km error-free transmission in straight line without forward error correction (FEC) and electric regeneration was demonstrated in this paper to evaluate the performance of modified CSRZ, and chirped fiber Bragg grating (CFBG) employed as the dispersion compensator in this transmission system. The experiment
result showed that if the modified CSRZ format was applied in this 2560km transmission, less than 2.5dB power penalty was cost after 2560km transmission, and on the other hand, error-free transmission could not be got in the conventional NRZ-based CFBG-compensated system.
Using dispersion compensation CBG, 2500km-10Gbps RZ and CSRZ transmission system on G.652 fiber is successfully demonstrated without electric regenerator and without Raman amplifier. At 2080km and 2560km, power penalty for RZ is about 3dBm and 5dBm (condition: RZ signal, BER=10-12, PRBS=1023-1); And power penalty for CSRZ is about 1dBm and 3dBm. The result indicates it is superior to the system using CSRZ signal under same condition.
Group velocity delay ripple (GDR) and reflectivity ripple (RR) are the main nonideal characteristics for chirped Bragg fiber grating (CFBG). The influence of these nonideal characteristics on the CFBG-based transmission systems with carrier suppressed return-to-zero (CSRZ) format was investigated, and the performance of the transmission system was evaluated by the eye opening penalty (EOP) in this paper. In additional, the impact of the phase difference between the central wavelength of the transmitted signal and the GDR on the transmission system which make the transmission performance fluctuate randomly was also studied. The analysis helps to conduct a practical 10Gb/s 2560km error-free transmission experiment in straight line with low power penalty, and no electronics regenerator and forward error correction (FEC) were employed in this system. The experiment result is so attractive in long haul transmission field.
We report on a 40 Gbit/s NRZ (non-return-to-zero) code transmission experiments including an dynamic Polarization mode dispersion (PMD) compensation. The dynamic PMD compensator is made up of two-stage four degrees. The first stage adopts polarization controller and fixed time-delayed line. The second stage is variable Differential Group Delay (DGD) element. The PMD monitoring technique is based on degree of polarization (DOP) as error signal. A novel practical adaptive optimization algorithm was introduced in dynamic adaptive PMD compensation. The experimental results show that the performance of the PMD compensator is excellent for 40Gbits/s NRZ transmission systems with the large the DGD. With this compensator, a significant improvement of system performance can be achieved in the eye pattern of a received signal.
Dynamic programming, the ordinary adaptive compensation in the operational research, is used to resolve extremum of functions under the constraint condition. In this paper, it is introduced that, fundamentals, methods and steps about the first-order PMD compensation by dynamic programming. The result shows that, for the first-order PMD compensation, dynamic programming is used to carry out optimized design, and the result is satisfied. Beginning with recursive relation of PMD vectors in the fiber and the compensation devices, mathematical model of the first-order PMD compensation is established. Through optimized algorithm using dynamic programming, simulation and experiment for PMD adaptive compensation are both implemented. Some optimized algorithms once used in the PMD adaptive compensation have slow speed to approximate the optimal value and tends to become the local optimal solution; but if optimized algorithm using dynamic programming can approximate the global optimal solution directly. Therefore, it has the advantage of fast optimized speed. On this basis, the image of optimal solution is given and analyzed. PMD compensation scheme, based on PMD compensation vector, is proposed. The algorithm principle of adjusting control and the direction of improvement are also put forward. These results are benefit for dynamic adaptive compensation of PMD.
A novel wavelength-routing all-fiber 10Gb/s WDM network with four nodes in a ring topology is forwarded, and at each node data can be transmitted at different wavelength according to the destined node which it wants to transmit. The main character of the system is that the stable-packed chirp fiber Bragg gratings (CFBG) used in this network utilize two functions: route and dispersion compensation. Meanwhile, a modified measuring method of power penalty including cross-talk penalty, ASE penalty and dispersion penalty is illustrated, and the experiment conducted in this paper shows the measuring method can be perfectly applied in this wavelength-routing all-fiber WDM network system mentioned above. All these measures ensure that optimum system performance would be achieved.
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