New method of data regeneration for multigigabit/s lightwave systems

Transmission of 2.5 Gbit/s spectrum-sliced fibre amplifier light source channels over 200 km of dispersion-shifted fibre (DSF) has been achieved, the highest bit-rate distance product 500 Gbit/skm using incoherent light sources reported to our knowledge. The total power penalty was as low as 0.2 dB for the 1.8 nm bandwidth channel centred at the zero-dispersion wavelength of DSF.

Everyone in the world always wants to use a better wireless network which provide high capacity and high data rates. High data rates and capacity can be produce by Multiple Input Multiple Output(MIMO) systems. This paper mainly focused on MIMO systems because the MIMO systems have multiple number of antennas in transmitting and receiving end which can produce more data rates and capacity compared to SISO, SIMO, MISO systems. The multiple antennas allow MIMO systems to produce multiplexing gain and diversity gain. The capacity of MIMO systems will be increased by increased the number of antennas in transmitter and receiver end.

A tunable Brillouin multi-wavelength mode-locked fiber laser (BMMFL) is proposed, predominantly based on a nonlinear optical loop mirror (NOLM) and assisted by nonlinear polarization rotation (NPR). The system employs 10 km of dispersion-shifted fiber (DSF) as the Brillouin gain medium to generate multiple wavelengths. The DSF, together with the polarization controller (PC1) and the optical coupler (OC1), forms the NOLM; the combined NOLM-NPR action functions as an equivalent saturable absorber (SA) to enable mode-locked pulse generation. By adjusting the PCs, the BMMFL generated 69 Brillouin multi-wavelength lines (BMLs) with a 10.9 GHz Brillouin frequency shift, when the pump power, Brillouin pump (BP) power, and BP central wavelength were fixed at 250 mW, 6 dBm, and 1546.5 nm, respectively. Under these conditions, no stably repeating mode-locked pulses were observed. A multi-wavelength tuning range of 30 nm was also obtained at different BP central wavelengths. Subsequently, by further adjusting the PCs, the BMMFL achieved a mode-locked pulse train with a pulse width of 236 ns and a fundamental frequency repetition rate of 19.92 kHz, with only 13 BMLs retained. At a pump power of 350 mW, the maximum average output power of the mode-locked pulse reached 1.29 mW. Moreover, harmonic mode locking up to the fifth order was achieved. This BMMFL offers broad application prospects in dense wavelength division multiplexing (DWDM) systems, laser processing and optical fiber communications.

The authors present, for the first time, 32/spl times/10 Gbit/s transmission (50 GHz channel spacing) in the zero-dispersion region of dispersion-shifted fibre (DSF) by employing multiwavelength distributed Raman amplification. Each transmission span is bi-directionally pumped at two wavelengths, 1450 and 1465 nm, to construct a wideband distributed Raman amplifier. A hybrid amplifier formed by a gain-flattened erbium-doped fibre amplifier and a gain-flattened distributed Raman amplifier is used to successfully realise dense WDM transmission in the zero-dispersion region over 8/spl times/80 km of DSF.

Future Wireless communication systems have to be designed to integrate features such as high data rates, high quality of service and multimedia in the existing communication framework. Increased demand in wireless communication systems has led to the demand for higher network capacity and performance. Higher bandwidth, optimized modulation offer practically limited potential to increase the spectral efficiency. Hence MIMO systems utilizes space multiplex by using array of antenna’s for enhancing the efficiency at particular utilized bandwidth. MIMO use multiple inputs multiple outputs for a single channel. These systems are defined by spectral diversity and spatial multiplexing. MIMO describes the ways to send data from multiple users on the same frequency/time channel using multiple antennas at the transmitter and receiver end. A transmitter/receiver system uses multiple antennas not only for transmitting data between corresponding antennas but also between adjacent antennas. The data is received in the form of MIMO Channel Matrix. A top level MIMO system (Joseph et al., 2007) is shown in Fig.1.1. MIMO system is used in many applications like WiMax, Wi-Fi, WLANs, and many more applications.

Minimally-invasive implanted devices usually transmit both power and data through inductive coupling. By separating power and data carriers into different frequency bands, a high data rate can be transmitted without affecting power link efficiency. However in a dual band approach, the electromagnetic field from the power link interferes with data transmission. This paper presents a high data rate Differential Phase Shift Keying (DPSK) telemetry designed to tolerate interference without electromagnetic shielding or a high-order filter. On the transmitter side, by analyzing the nature of the interference, "frequency pre-distortion" is introduced to maintain the maximum efficiency. On the receiver side, a differential scheme is employed to provide inherent interference rejection. Using subsampling and novel analog demodulation, the scheme also eliminates the requirement of carrier recovery, thus reducing circuit complexity. The receiver achieves a 1Mbps data rate and can be upgraded to 2Mbps.

The demand for high data rate applications is on the rise in the recent years which is due to the rapid growth in wireless communication. The existing technologies like Wireless Fidelity (Wi-Fi) and Bluetooth cannot support such high data rates because of their narrowband and also they drain the battery at rapid pace. Ultra Wide Band (UWB) system differs from conventional narrow band system by transmitting short duration pulses occupying a large bandwidth with power levels almost comparable to that of the noise floor. Any communication technology which uses more than 500 MHz of bandwidth in the range of 3.1 to 10.6 GHz is defined as UWB. The transmitter side of impulse radio consists of pulse generator and modulator. The pulse generator is used to generate the required short pulse in the desired range of frequency. The proposed pulse generator is of pulse combination type impulse generator which is fully digital constructed with MOS Current Mode Logic (MCML) as Fine Delay Elements without using passive components thus reducing circuit complexity. The proposed pulse generator is designed using 90 nm technology with 1 V supply voltage. The maximum power consumption is 330 μW. The output voltage shape complies with FCC regulation.

A popular research topic as of late has been dynamic partial FPGA (Field Programmable Gate Array) reconfiguration. This concept allows on-the-fly reconfiguration of digital systems where only parts of the circuit change, providing application acceleration and allowing static modules to continue processing unaffected by the dynamic elements. Design characteristics which benefit from this progressive approach include increased system flexibility, increased performance, and a reduction in circuit complexity. One characteristic receiving limited focus thus far has been the increased security that could result from these changing circuits. This benefit is innate to the design and makes reverse engineering of the system a much more ambitious task. In an effort to further enhance this passive security feature, a new partial reconfiguration technique has been proposed that changes connectivity between generic modules. This extended abstract introduces the method, model, and design flow for this dynamic partial FPGA reconfiguration technique and addresses the security implications of such a design.

The regeneration of optical data signals is an important requirement of WDM and OTDM networking schemes. All-optical regenerators based on cross phase modulation schemes currently require complicated systems of several optical components and modules together with complex control. Here we demonstrate an optical 3R regeneration in a single DFB laser. The key to this regeneration process is to gain switch the DFB laser with a clock signal extracted from the data signal in order to retime the converted signal. A data signal at 10Gbits/s sent to 80Km in a SMF with poor Q is reamplified, retimed and reshaped by this laser. However the uncorrelated jitter (amplitude and phase noise) primarily present due to the spontaneous emission in the directly modulated transmitting laser as well as in the gain switched DFB laser (Regenerator) can very easily distort the whole regeneration process. In this paper we propose a systematic approach to tackle this problem to effectively enhance the performance of optical regenerator. An improvement of orders of magnitude in BER measurement can be achieved. The proposed approach results in a regenerated signal whose optical power, Q factor and extinction ratio are considerably improved by the regeneration process.

An interchannel parallel coding scheme in the wavelength domain/spl minus/the WDM coding system/spl minus/is proposed. The system differs from the usual serial coding systems and provides many advantages. First, data channels are completely unaltered in the coding process, rendering it very suitable for practical lightwave systems with standard bit rate. Second, parallel encoding/decoding systems are simpler than those of serial coding systems, being easier to be implemented in high-speed optical systems. Third, compared with serial coding, WDM coding is able to reduce heavily the number of encoding/decoding pairs. For example, a (15, 11) Hamming coded WDM system reduces the number from 12/spl times/11=132 to 1 at the line rate of STS-12. Fourth, the WDM coding system could offer infinite coding gain in dispersion-limited lightwave systems. Finally, WDM coding systems could correct single-channel burst error. The system performance was evaluated and the system limitation imposed by bit-skew among wavelength channels was analyzed. The results indicated that a 15-channel Hamming coded WDM system can reduce the uncoded BER from 10/sup /spl minus/9/ to 3/spl times/10/sup /spl minus/17/ and the distance limitation imposed by bit-skew is 250 km if a dispersion-shifted fiber is used and a channel span of 30 nm is assumed. >

The paper describes the efficient CMOS technology based current source for system identification and it's layout realization with reduced circuit complexity. Square wave excitation current is preferred in energy constrained and embedded environment. It has been shown that by shortening the square waves, spectral purity of the excitation signals can be drastically improved. Further improvement can be achieved by introducing limited number of additional equally spaced current levels. The basic idea of such a solution is that by suitably adding several simple shortened pulses together some of the high energy harmonics are either further reduced or eliminated. This multilevel signal can be easily generated digitally and it enables simpler digital processing involving only additions and shifting. On the other hand required extra circuitry for multiple current levels should not eliminate main advantages of square wave excitation, such as reduced complexity and low consumption. Proposed solution improves the power consumption and reduces the complexity of the system as a whole compared to more generic approach. The current source output will be the shortened multilevel square wave signal. The output current value can be selected from range from 5 to 100 μA. The main advantage of this method is greater efficiency because for measuring cycle only one or two pairs of switchable current mirrors will be activated to drive the H-bridge.

The paper focuses on fault diagnosis in nonlinear analog circuits, a topic that has been explored in the literature for over 50 years but remains unresolved due to its complex nature. It reviews various aspects of nonlinear circuit diagnosis, including methods for assessing testability, selecting diagnostic tests, and conducting diagnostic processes through simulation before and after test methods. The paper also discusses the use of artificial intelligence tools in this context. Given the specific characteristics of nonlinear circuits used as DC-DC converters and the wealth of the existing literature—including review papers on the subject—this issue is addressed only briefly. The main aim of the paper is to identify research challenges in fault diagnosis for a general class of nonlinear circuits. To illustrate and discuss these challenges, the paper provides examples, including ambiguity in diagnostic equation solutions, multiple equilibrium points, and the effects of self-heating. These examples can serve as simple benchmarks for new proposals to advance comprehensive diagnosis methods for nonlinear circuits.

In this paper, a compressed sensing based scalable video coding using discrete wavelet transform (DWT) for space applications is presented. The proposed method is aimed at reducing the requirement of on-board memory, station contact time and data archival volume. Compressive sensing (CS) has been applied to encode the distributed wavelet coefficients into linear measurements. Since prior knowledge of the compressively sampled measurements is not available, a modeler is employed to determine the context of the measurement vector. Based on the statistics provided by the context modeler, the samples are entropy coded for transmission. A part of the compressive sampling measurements with near uniform distribution are encoded through adjusted binary coding, and the rest are encoded through Golomb-Rice coding. Run length encoding is implemented for exploiting the redundancy in the binary data further. At the receiver end, the original spatial signal is reconstructed from the CS samples by approximate message passing (AMP) algorithm and inverse discrete wavelet transform (IDWT) for video decompression. Simulation of the proposed approach has demonstrated an efficient compression of the video cubes with lower complexity at the transmitter end.

OPTICAL COMMUNICATIONS USING SURFACE ACOUSTIC WAVES

In this paper, a microwave photonic dual band radar based on a photonic-assisted de-chirp processing receiver is proposed. The dual band operation is realized independently and simultaneously with a single set of hardware. At a transmitter end, two linear frequency-modulated signals separately located in C-band and Ku-band are transmitted, echoes are collected and sent to a receiver to implement photonic-assisted de-chirp processing. At the receiver end, a main modulator with a special structure, which consists of four parallel sub-modulators, is employed. The echoes and reference signals of C-band and Ku-band are applied to two pairs of sub-modulators of the main modulator, which are biased at the peak points for C-band and biased at the null points for Ku-band. In this case, the intermediate frequency signals of C-band and Ku-band produced by de-chirp processing locate at two different frequencies. Thus operation in different bands based on a unified system is achieved. An experiment operating in C-band and Ku-band with a bandwidth of 700 MHz and 3600 MHz is conducted. The results verify the concept of the dual band radar and show the potential of photonic technology to improve the performance of modern radar system.