Nonlinear Liquid Crystal Optical Signal Amplifiers

The principle, structure and system of nonlinear liquid crystal optical signal amplifiers are described. Experimental results are theoretically analysed for optical signal amplifers. It shows that this type of the optical signal amplifiers are comprised of liquid crystal light sensitive medium which can receive a modulated signal optic wave and a pump wave, and can be applied to optical transmission systems.

Design of Diode Type Un-Cooled Infrared Focal Plane Array Readout Circuit

The diode infrared focal plane array uses the silicon diodes as a sensitive device for infrared signal measurement. By the infrared radiation, the infrared focal plane can produces small voltage signals. For the traditional readout circuit structures are designed to process current signals, they cannot be applied to it. In this paper, a new readout circuit for the diode un-cooled infrared focal plane array is developed. The principle of detector array signal readout and small signal amplification is given in detail. The readout circuit is designed and simulated by using the Central Semiconductor Manufacturing Corporation （CSMC） 0.5 μm complementary metal-oxide-semiconductor transistor （CMOS） technology library. Cadence Spectre simulation results show that the scheme can be applied to the CMOS readout integrated circuit （ROIC） with a larger array, such as 320×240 size array.

Optical Nonlinearity in a Novel Optical Signal Regeneration System Based on Cross-Gain Modulation Using Cascaded Semiconductor Optical Amplifiers

We propose a novel optical signal regeneration system based on wavelength converters by use of cross gain modulation in cascaded semiconductor optical amplifiers. The nonlinearity in optical input/output characteristics and eye opening using NRZ signal were archived.

Fiber-based optical parametric amplifier for 40-Gb/s NRZ-DPSK signal transmission system employing QC-LDPC codes

In this letter, we investigate quasi-cyclic low-density parity-check （QC-LDPC） codes in a 40-Gb/s nonreturn-to-zero differential phase-shift keying （NRZ-DPSK） signal transmission system based on a fiber- based optical parametric amplifier （FOPA）. A constructed algorithm of QC-LDPC codes according to the optimizing set of shift vMues on the circulant permutation matrix （CPM） of the basis matrix is proposed. Simulation results prove that the coding gain in the encoded system can be realized at 10.2 dB under QC- LDPC codes with a code rate of 5/6 when the bit error rate （BER） is 10-9. In addition, the error-floor level originating from the uncoded system is suppressed.

Low power CMOS preamplifier for neural recording applications

A fully-differential bandpass CMOS （complementary metal oxide semiconductor） preamplifier for extra- cellular neural recording is presented. The capacitive-coupled and capacitive-feedback topology is adopted. The preamplifier has a midband gain of 20.4 dB and a DC gain of 0. The -3 dB upper cut-off frequency of the preamplifier is 6.7 kHz. The lower cut-off frequency can be adjusted for amplifying the field or action potentials located in different bands. It has an input-referred noise of 8.2 μVrms integrated from 0.15 Hz to 6.7 kHz for recording the local field potentials and the mixed neural spikes with a power dissipation of 23.1μW from a 3.3 V supply. A bandgap reference circuitry is also designed for providing the biasing voltage and current. The 0.22 mm2 prototype chip, including the preamplifier and its biasing circuitry, is fabricated in the 0.35-μm N-well CMOS 2P4M process.

Performance improvement by enhancing the well-barrier hole burning in a quantum well semiconductor optical amplifier

In this paper, we demonstrated a novel physical mechanism based on the well-barrier hole burning enhancement in a quantum well （QW） semiconductor optical amplifier （SOA） to improve the operation performance. To completely characterize the physical mechanism, a complicated theoretical model by combining QW band structure calculation with SOA＇s dynamic model was constructed, in which the carrier transport, interband effects and intraband effects were all taken into account. The simulated results showed optimizing the thickness of the separate confinement heterostructure （SCH） layer can effectively enhance the well-barrier hole burning, further enhance the nonlinear effects in SOA and reduce the carrier recovery time. At the optimal thickness, the SCH layer can store enough carrier numbers, and simultaneously the stored carriers can also be fast and effectively injected into the QWs.

A small signal coupling model for predicting the coupling between LNAs

A small signal coupling model is developed to analyze the coupling between two LNAs. The mutual inductance between the adjacent on-chip inductors is considered responsible for this coupling. A set of formulas have been derived to quantitatively predict the coupling effects. Based on our analysis, a quick estimation can be made to see which pair of inductors plays a key role in evaluating the coupling between the LNAs. Source inductors of two LNAs are placed closely while the load inductors are far apart according to the analysis. To validate the proposed theory, two 2 GHz LNAs are fabricated. The LNAs have a peak gain of 18 dB and NF of 1.4 dB. The coupling between the LNAs is –30 dB.

Ultra-low noise measurements of nanopore-based single molecular detection

Nanopore is an ultra-sensitive electrochemical technique for single molecular detection in confined space. To suppress the noise in detection of the weak current of nanopore, we investigated the influence of membrane capacitance and applied voltage on the noise of the current signal by model analysis, simulation and experiment. The obtained results demonstrated that membrane capacitance affects the noise by amplifying the noise of the applied voltage. Therefore, suppression of applied voltage noise is an efficient approach for reducing the noise in nanopore detection. Here, we developed an ultra-low noise instrument system for detecting the single molecule signal in nanopores. As demonstrated by nanopore experiments, the p-p noise of the developed system during the recording is reduced to 3.2B pA using the filter of 5 kHz. Therefore, the developed system could be applied in highly sensitive nanopore detection.

A multi-channel analog IC for in vitro neural recording

Recent work in the field ofneurophysiology has demonstrated that, by observing the firing characteristic of action potentials （AP） and the exchange pattern of signals between neurons, it is possible to reveal the nature of ＂memory＂ and ＂thinking＂ and help humans to understand how the brain works. To address these needs, we developed a prototype fully integrated circuit （IC） with micro-electrode array （MEA） for neural recording. In this scheme, the microelectrode array is composed by 64 detection electrodes and 2 reference electrodes. The proposed IC consists of 8 recording channels with an area of 5 x 5 mm2. Each channel can operate independently to process the neural signal by amplifying, filtering, etc. The chip is fabricated in 0.5-#m CMOS technology. The simulated and measured results show the system provides an effective device for recording feeble signal such as neural signals.

ABORT-like detector to combat active deceptive jamming in a network of LFM radars

This paper studies an electronic counter-counter measures（ECCM） scheme combating against deceptive electronic counter measure（ECM） techniques. An adaptive detector exploiting generalized likelihood ratio test（GRLT） criterion is applied to detect the presence of deceptive jamming in fractional Fourier transform（Fr FT） domain. First, the generating mechanism of spurious frequencies is analyzed based on the Volterra serial. The proposed nonlinear distortion model based on power amplifier behavior is robust in distortion analysis when the memory effect is considered.Second, a modified adaptive beamformer orthogonal rejection test（ABORT） like detector in closed form is built. The proposed detector can discriminate the echo and deceptive jamming adaptively by exploiting primary data and secondary data. This ECCM scheme is capable of guaranteeing the performance without the restriction of orthogonality, which is essential for the ABORT detectors. The expansion to radar network is discussed as a special case at the final part of this paper. Numerical simulations demonstrate the effectiveness of the proposed method.

All-optical NRZ wavelength conversion using a Sagnac loop with optimized SOA characteristics

We investigated the all-optical wavelength conversion technique for non-return-to-zero（NRZ） signals based on a Sagnac loop interferometer using an SOA. For the wavelength conversion of the NRZ signal at and above40 Gbit/s, we used an in-house numerical SOA model to analyze the influence of the SOA carrier characteristics and the SOA length on the performance of the Sagnac loop. We found that the SOA carrier recovery time should be between 2 and 3 times of one bit duration in order to get optimum NRZ wavelength conversion. In addition to the carrier recovery time requirement, SOAs with a shorter physical length are preferred to be used in the Sagnac interferometer.