Good Eye Opening Research Articles

Performance analysis of DP-MZM radio over fiber links against fiber impairments

Abstract In this research article, the radio over fiber (RoF) Architecture using dual-parallel Mach–Zehnder modulator (DP-MZM) is analyzed and simulated. The nonlinearity is the main issues which degrade the performance of the RoF links. Using DP-MZM modulators, the nonlinearity can be reducing in the significant amount by controlling the bias voltages. The DP-MZM consists of two MZM modulators in parallel form with the variations of extinction ratio (ER). The proposed RoF link operated with single tone frequency signal at 10 GHz and the optical signal is transmitted further on Single mode optical fiber. The electrical spectrum at the output of photodetector confirms the quality of received signal while having desired and undesired terms. The proposed structure is designed using Optical Simulator simulation Software to confirm and validate the proposed results. The simulation output shows that the RF power of DP-MZM based RoF link has been found a decrement of 6.95 dB corresponding to undesired components with respect to desired RF signal for the increment in fiber length from 10 to 30 km. The digital transmission RoF link model is proposed and optimized for fiber impairments for 2–30 km, using 10 Gbps digital data string. electrical spectrum analyzer shows that very good eye openings for different fiber impairments, its shoes that proposed RoF model is optimized and having good SNR.

Enhanced tolerance against optical background noise in VLC link by using line coded signal with receiver filter

The performance of visible light communication (VLC) link is significantly affected by optical background noises generated by fluorescent light or AC driven light emitting diode (LED) and eventually degrades the data rate due to the in-band interference between signal and noise. Here, bandwidth efficient 8b10b dc-balanced line coding and post-detection electrical filter based VLC link is demonstrated to improve the system tolerance against the optical background noises. The 8b10b coded signal with low frequency components near DC ensure that the crosstalk noise is effectively minimized by spectral separation of signal and noise contributions. Moreover, the use of post detection filter for 8b10b coded signal gives an additional attenuation of noise frequency to further improve the system tolerance against optical background noise. The proposed VLC link is investigated thoroughly in several noise power levels as well as different noise frequencies, where the results indicate improved system tolerance against noise power by about 6.5 dB in compare to conventional data signal. The demonstration also shows that the proposed scheme maintains a low BER for the noise frequency up to 500 kHz for 10 Mb/s data modulation having a good eye opening.

NDR-effect vertical-illumination-type Ge-on-Si avalanche photodetector.

We present the enhanced performances of a vertical-illumination-type Ge-on-Si avalanche photodetector based on internal RF-gain effects operating up to 50 Gb/s. A fabricated Ge-on-Si avalanche photodetector (APD) exhibits three operational voltage regions associated with different aspects of the current (DC) gain and bandwidth characteristics. The measured current-voltage (I-V) curve of a Ge-on-Si APD exhibits a negative photoconductance (negative differential resistance [NDR]) in a high bias region beyond the avalanche breakdown voltage (V br ), where a device shows good eye openings up to 50 Gb/s (non-return-to-zero [NRZ] signal) with further improved signal-to-noise ratios and signal amplitudes. A ROSA packaged module, wherein a fabricated Ge-on-Si APD is wire-bonded to a commercial TIA with a ∼75% optical alignment for λ∼1310 nm and biased at a lower voltage than the V br , exhibits the sensitivities of -18.9 and -15.3 dBm for 30 and 35 Gb/s, respectively, and -13.9 dBm for 40 Gb/s at a 10-12 bit error rate. The experimental results indicate that considerable improvement in a module performance can be expected by utilizing the Ge-on-Si APD operated in the NDR region with a properly customized TIA.

Comparative investigation and suitability of various data formats for 10 Gb/s optical AWG multiplexer and AWG demultiplexer based transmission links

In this paper, we have analyzed the performance and feasibility for the metropolitan area network based on arrayed waveguide grating (AWG) multiplexers and arrayed waveguide grating (AWG) demultiplexers operating at the bitrate of 10 Gb/s. In the network, the data is successfully transmitted to a distance of 50 km with a very low BER of 1 × 10 −40 thus improving the performance over AWG star based networks. Here, we have observed that arrayed waveguide gratings based multiplexers and demultiplexers for WDM applications prove to be capable of precise multiplexing and demultiplexing of a large number of channels with relatively low losses. This paper also presents the comparative investigation and suitability of various data formats like NRZ Rectangular, NRZ Raised cosine, RZ Rectangular, RZ Raised cosine and RZ super Gaussian for optical transmission link. It has been shown that RZ Raised cosine yields the highest value of Q, good eye opening and lowest BER.

Compensating spectral loss variations in EDFA amplifiers for different modulation formats

In this paper, we investigate the performance of the optical system consisting of chain of EDFA amplifiers for different data formats such as non-return-to-zero (NRZ), return to zero (RZ) and Manchester. Their effect on the spectral loss variations produced in fiber output is analyzed. We show that when the RZ raised cosine and Manchester raised cosine modulation formats are used, the non-linear ties are produced in power spectrum plots which severely distort the signals obtained at the output of the chain of the EDFA amplifiers. On the other hand, the NRZ raised cosine modulation format best compensates the spectral loss variations in the power spectrum plots obtained at the output. We further show that NRZ raised cosine has good eye opening as compared to other modulation formats.

Fabrication of Transimpedance Amplifier Module and Post-Amplifier Module for 40 Gb/s Optical Communication Systems

The design and performance of an InGaAs/InP transimpedance amplifier and post amplifier for 40 Gb/s receiver applications are presented. We fabricated the 40 Gb/s transimpedance amplifier and post amplifier using InGaAs/InP heterojunction bipolar transistor (HBT) technology. The developed InGaAs/InP HBTs show a cut-off frequency (fT) of 129 GHz and a maximum oscillation frequency (fmax) of 175 GHz. The developed transimpedance amplifier provides a bandwidth of 33.5 GHz and a gain of 40.1 dBΩ. A 40 Gb/s data clean eye with 146 mV amplitude of the transimpedance amplifier module is achieved. The fabricated post amplifier demonstrates a very wide bandwidth of 36 GHz and a gain of 20.2 dB. The post-amplifier module was fabricated using a Teflon PCB substrate and shows a good eye opening and an output voltage swing above 520 mV.

A novel reconfigurable optical interconnect architecture using an Opto-VLSI processor and a 4-f imaging system

A novel reconfigurable optical interconnect architecture for on-board high-speed data transmission is proposed and experimentally demonstrated. The interconnect architecture is based on the use of an Opto-VLSI processor in conjunction with a 4-f imaging system to achieve reconfigurable chip-to-chip or board-to-board data communications. By reconfiguring the phase hologram of an Opto-VLSI processor, optical data generated by a vertical Cavity Surface Emitting Laser (VCSEL) associated to a chip (or a board) is arbitrarily steered to the photodetector associated to another chip (or another board). Experimental results show that the optical interconnect losses range from 5.8dB to 9.6dB, and that the maximum crosstalk level is below -36dB. The proposed architecture is tested for high-speed data transmission, and measured eye diagrams display good eye opening for data rate of up to 10Gb/s.

Analysis of high bit rate operation of a vertically gain-clamped semiconductor laser amplifier

A detailed theoretical model of the high bit rate operation of a vertically gain-clamped semiconductor optical amplifier with high bit rate return-to-zero and non-return-to-zero input signals is presented. It is shown that good eye opening at 10–40 GBit/s can be achieved at sufficiently high operating currents (hundreds of mA in a realistic construction). A resonance between the relaxation oscillations of the vertical laser and the bit rate of the input signal is detrimental to the amplifier performance and should be avoided. When designing the length of the amplifier, a trade-off exists between the eye opening and the average gain.

Comparative investigation and suitability of various data formats for 10 Gb/s optical soliton transmission links at different chirps

This paper presents the comparative investigation and suitability of various data formats for optical soliton transmission links at 10 Gb/s for different chirps (−0.7 to 0.7). Here the investigations focused on data formats: NRZ, RZ soliton, RZ raised cosine and RZ super Gaussian. The comparative results and suitability of data formats is based on various performance measures such as Q-factor, eye opening, BER and jitter. It has been indicated that RZ super Gaussian yields the highest value of Q (34.08 dB), good eye opening and lowest BER.

High gain-bandwidth differential distributed InP D-HBT driver amplifiers with large (11.3 V/sub pp/) output swing at 40 Gb/s

High-performance and compact 40-Gb/s driver amplifiers were realized in 1.2-/spl mu/m emitter double-heterojunction InGaAs-InP HBT (D-HBT) technology with a maximum cut-off frequency (f/sub T/) of 150 GHz and a maximum oscillation frequency (f/sub max/) of 200 GHz. Two-stage differential drivers feature a lumped input and fully distributed output stage and deliver a maximum differential output swing of 11.3 V peak-to-peak (V/sub pp/) at 40 Gb/s with less then 350 fs of added rms jitter and rise and fall times of about 7 ps while consuming a total power of 3 W. When biased at a lower output swing of 6.3 V/sub pp/, excellent 40-Gb/s eyes with a 7-ps fall time, 6-ps rise time, and no observable jitter deterioration compared with the input source are obtained at a reduced power consumption of 1.7 W. On-wafer measured differential S-parameters show a differential gain of 25 dB, 50 GHz bandwidth, and input and output reflection below -20 dB from 2 to 45 GHz. The amplifiers' small die size (1.0/spl times/1.7 mm), relatively low power consumption, large output swing, and ability to have dc coupled inputs and outputs enable compact 40-Gb/s optical transmitters with good eye opening for both conventional transmission formats such as nonreturn-to-zero and return-to-zero and alternative formats such as duobinary and differential phase shift keying.

Bit-rate and format conversion from 10-Gbit/s WDM channels to a 40-Gbit/s channel using a monolithic Sagnac interferometer integrated with parallel-amplifier structure

Full bit-rate conversion from 10-Gbit/s random wavelength-division multiplexing (WDM) channels to a 40-Gbit/s channel, including non-return-to-zero (NRZ) to return-to-zero (RZ) format conversion and reconversion, was successfully demonstrated. The key technique is wavelength conversion using a monolithic Sagnac interferometer integrated with a parallel-amplifier structure. Good eye-openings through the 10-Gbit/s NRZ to 40-Gbit/s RZ, and 40-Gbit/s RZ to 10-Gbit/s NRZ conversions were obtained. Error-free operation and a small power penalty of less than 0.8 dB were achieved. Phase adjustment of 10 Gbit/s signals was also successfully demonstrated with slight wavelength conversions using a planar lightwave circuit and semiconductor optical amplifier hybrid integrated Mach–Zehnder inteferometer.

High quality 80 Gbit/s InP DHBT selector and its use for NRZ-RZ conversion

A high speed selector IC fabricated in self-aligned InP DHBT technology is presented. Circuit measurements at 80 Gbit/s (measurement setup limitation) show very good eye opening (0.56 ps RMS time jitter, low rise and fall times). Circuit operation as 40 Gbit/s NRZ to RZ converter was also characterised.

Light emission and detection characteristics of GaInAsP lateral current injection lasers for planar optoelectronic integrated circuits

The light emission and detection characteristics of a GaInAsP lateral current injection (LCI) laser were studied to examine feasibility for optoelectronic functional devices. LCI lasers which can be fabricated on semi-insulating substrates in quasi-planar structures are very appropriate for integration with electronic devices, and are promising light sources for optoelectronic integrated circuits (OEICs). For the light emission characteristics, the LCI laser has a modulation bandwidth above 2 GHz. Also, good eye openings at 1-Gb/s signals is confirmed for the laser in eye diagrams for pseudorandom bit stream input signals. For the light detection characteristics, the 3-dB detection bandwidth of more than 2 GHz, high responsivity of 0.54 A/W, and small polarization dependence of 0.17 dB are confirmed. These performances show that the LCI laser might be a good candidate for the light emission and detection diode in OEICs in future.

High-speed all-optical AND gate using nonlinear transmission of electroabsorption modulator

We investigated an all-optical logic AND operation at 10 Gb/s using nonlinear transmission of electroabsorption modulator pumped with two counterpropagating data streams. The transmitted pump itself was used as the output of the optical gate to obtain high extinction ratio, and high-output peak powers. The gate has been tested using 2/sup 31/-1 long pseudorandom bit sequence. The logical output of the gate has an extinction ratio of more than 10 dB with good eye opening. Our measurements of the gate transmission window show that all-optical logic operation up to 100 Gb/s is feasible.

5 Gbit/s laser-driver GaAs IC

A design of a 5 Gbit/s laser-driver GaAs IC employing a novel 50 Ω impedance matched output driver is presented. Eye diagrams with good eye openings, clean waveforms and output reflection coefficients of less than –8 dB for frequencies up to 10 GHz are demonstrated over a 10–36 mA output current tuning range.

20 Gb/s digital SSIs using AlGaAs/GaAs heterojunction bipolar transistors for future optical transmission systems

Design principles for achieving good eye opening and circuit optimization to extract high performance from AlGaAs/GaAs heterojunction bipolar transistor (HBT) devices are described. Using the circuit techniques and HBTs with an f/sub T/ of 70 GHz and an f/sub max/ of 50 GHz, four kinds of SSIs are developed for future optical transmission systems. High-bit-rate operation of over 20 Gb/s (26 GHz toggle flip-flop, 20 Gb/s decision circuit, 20 Gb/s EXCLUSIVE OR/NOR gate, and 28 Gb/s selector IC), extremely fast rise and fall times (20-80%) of 20 and 14 ps, respectively, and good eye opening are obtained. In addition, potential performance gains that might be realized through advanced circuit and device design are appraised, and throughputs as fast as 40 Gb/s are predicted.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

3 Gbit/s two-level to 1.5 Gsymbol/s four-level convertor GaAs IC for two electrode semiconductor optical amplifier modulators

A novel design of a 50 Omega impedance model matched two-to-four level convertor GaAs IC for two electrode semiconductor optical amplifier modulators is presented. Eye diagrams with good eye openings and 0.33 V spacing between adjacent logic levels are demonstrated for bit rates up to 3 Gbit/s. >