Volume 32, Issue 3

The performance of a all-optical header extraction scheme using semiconductor optical amplifier and Mach–Zehnder-Interferometer (SOA-MZI) with bidirectional data injection was studied at the packet rate of 80 Gb/s for ultrafast all-optical packet switching networks. Numerical analysis and simulation results showed that the contrast ratio of optical header extraction could exceed 18dB when input signal energy was as low as 0.1 pJ. In addition, the parameters of SOA-MZI and the input signal features were discussed to optimize the performance of proposed scheme.

A compound modulation diffraction grating is brought forward, and successful acting as a beam splitter. Compared with beam splitters made with this traditional single modulation grating, the beam splitter made with the compound modulated grating has some superiority on the error of optical parameters. And the model of the compound modulation diffraction grating can be applied to analysis the influence on diffraction efficiencies of the diffraction grating caused by the surface undulation.

In passively mode locked fiber laser, case of 8FL (Eight Fiber Laser), the management of length, linear and non linear parameters of the cavity plays a paramount role in the generation of stable ultra short pulses with high peak powers. In this work, we propose an 8FL consisted of MOF (Microstructured Optical Fiber). According to the various properties of the MOF, we studied the variation of the pulses peak power and width. We demonstrated that there are optimal parameters of the MOF for which the peak power is maximal and the width is minimal.

Impulse response characteristics of a semiconductor laser with weak optical feedback (OF) is studied. Equations about the amplitude and frequency responses of the laser under the current modulation condition are deduced. We demonstrate theoretically that the equations are the function of the modulation frequency, optical feedback level and delayed time. We give the impulse response function under the jump signal modulation condition with OF and without OF, this is helpful for digital laser communications. The numerical results demonstrated that OF can make the laser obtain the enhancement of the modulation response and bandwidth and can reduce the frequency respond in the some parameters range. OF can enhance gently the relaxation oscillation of the foreland or the tail of the impulse response signal under the weak OF case while the oscillation can be enhanced sensitivity to the modulation under the larger OF case

In this paper, a non-blocking multicast optical packet switch based on fiber Bragg grating technology with optical output buffers is proposed. Only the header of optical packets is converted to electronic signals to control the fiber Bragg grating array of input ports and the packet payloads should be transparently destined to their output ports so that the proposed switch can reduce electronic interfaces as well as the bit rate. The modulation and the format of packet payloads may be non-standard where packet payloads could also include different wavelengths for increasing the volume of traffic. The advantage is obvious: the proposed switch could transport various types of traffic. An easily implemented architecture which can provide multicast services is also presented. An optical output buffer is designed to queue the packets if more than one incoming packet should reach to the same destination output port or including any waiting packets in optical output buffer that will be sent to the output port at a time slot. For preserving service-packet sequencing and fairness of routing sequence, a priority scheme and a round-robin algorithm are adopted at the optical output buffer. The fiber Bragg grating arrays for both input ports and output ports are designed for routing incoming packets using optical code division multiple access technology.

In this paper, performance of incoherent and asynchronous optical CDMA (OCDMA) systems employing “optical encoding” is investigated and the results are compared with the results obtained when the encoding is performed in electrical domain. These investigations are performed for receiver structures that employ a single hard limiter (SHL), a double optical hard limiter (DHL) and also for the structures without a hard limiter (WHL). In addition, “electrical encoding” OCDMA systems using DHL in their receiver structures are investigated. In this work, conventional optical orthogonal codes are used and Gaussian approximation is assumed for the output of APD. Besides interference, other destructive effects such as APD and thermal noises are also taken into account. It is shown that when the number of users N is equal to or greater than pulsed laser's modulation extinction ratio M e , for all receiver structures (SHL, DHL and WHL) “optical encoding” systems are superior to their “electrical encoding” counterparts and this superiority becomes much more apparent in SHL and DHL receivers. We will also show that when N < M e , “optical encoding” WHL systems outperform their “electrical encoding” counterparts. Our results also indicate that the performance of “optical encoding” SHL systems approaches the performance of DHL systems as the transmitted power increases.

A colorless and bidirectional WDM-PON based on wavelength-locked RSOA technology is proposed. In this scheme, two service-ONUs in different wavelength bands are close to the user terminations. The broadband spectrum from either service-ONU is sliced by AWG located at the RN, and then the sliced lightwave is injected into the RSOA for upstream data. The system capacity can be doubled by adding some passive components at the RN. In simulation system, 2.5 Gb/s up/downstream data are transported successfully. In addition, transmission distance can be extended due to the less path loss of injected lightwave.

A model for the phase noise influence in differential n -level phase shift keying ( n PSK) systems and 2 n -level quadrature amplitude modulated (2 n QAM) systems employing electronic dispersion equalization and quadruple carrier phase extraction is presented. The model includes the dispersion equalization enhanced local oscillator phase noise influence. Numerical results for phase noise error-rate floors are given for dual polarization (DQPSK, D16PSK and D64PSK) system configurations with basic baud-rate of 25 GS/s. The transmission distance in excess of 1000 km requires local oscillator lasers with sub-MHz linewidth.

A scheme for half of the bandwidth of the en-/decoding spectrum application based on superstructured fiber Bragg grating (SSFBG) is presented in this paper. As verified by theoretical and simulation analysis, the half of the bandwidth of the en-/decoding spectrum has already contained all code information and en-/decoding function can be completed as long as the reflection spectrum covers half of the original bandwidth (half of the bandwidth of the en-/decoding spectrum). As indicated by the en-/decoding experiment, the en-/decoding performance of the half of the bandwidth of the en-/decoding spectrum application is better than that of the conventional mode of center alignment. The half of the bandwidth of the en-/decoding spectrum application shall choose half of en-/decoding spectrum inclining to Level 0, thus both ensuring auto-/cross-correlation of the en-/decoding and minimizing insertion loss. The half of the bandwidth of the en-/decoding spectrum application reduces costs for light sources and improves performance of the receiver, being conducive to the practical design of the system.