Two dimensional multistage AOCA system based on generalized equations has been analyzed. Numerical results for
Bragg angle as a function of acoustic frequency, deflection angles for different wavelengths, normalized power and
diffraction efficiency with and without phase shift between consecutive arrays having different channel spacing based on
generalized equations have been obtained.
The interaction of a fiber Bragg grating point like soliton with local defects has been thoroughly analyzed. The stability
of trapped solitons has also been discussed. The main finding reveals the reversal of the sign of interaction from
attraction to repulsion. It is also observed that the attraction depends on the accuracy of the numerical simulations.
One of the most promising devices for high speed optical signal processing is the Nonlinear Directional Coupler (NLDC). In this paper an asymmetric nonlinear directional coupler controlled by an external laser beam focused on the surface of the coupler has been analyzed. The analysis is based on couple-mode theory using rigorous perturbation technique and enables one to obtain asymptotically correct coupled-mode equations. The effects of various parameters such as plasma density, waveguide width, laser beam frequency and laser spot position on the coupling of power have been investigated and presented.
An optical switch based on micro electro mechanical systems (MEMS) technology has been analyzed and designed. In the proposed switch the collimating lenses as commonly used in MEMS switches have been eliminated thus making the switch smaller in size. The switch characteristics based on theoretical analysis and experimental results have been compared.
Current optical networks mainly serve very high data rates and long distances while short reach communication and low data rates is dominated by electrical interconnects. In this work, we examine and evaluate optical backplane technology based on substrate guided interconnects.
We investigated both experimentally and by simulation, non-return-to-zero (NRZ) and return-to-zero (RZ) 4-ary PAM operating at 20 Gb/s. A simple scheme to realize the quadratic signal leveling by suitably driving a MZ modulator is proposed, which provides greater than 6 dB improvement in receiver sensitivity as compared to equal level spacing. We experimentally demonstrated NRZ and RZ 10 Gbaud/s 4-ARY PAM transmissions over an 80 km standard single mode fiber (SSMF) link as a proof of concept and more detailed experimental results over longer reach will follow. Numerical simulations for the 4-ary PAM performance over longer distances (>200 km) are also presented.
Optical second harmonic generation in dense wavelength division multiplexing were used to monitor the performance of each channel in all optical networks. A poled Lithium-Niobate (PP-LNO3) device is used to convert C and L- Band optical WDM channels into half wavelength channels where silicon arrayed detectors and CMOS electronics were used to perform advanced digital signal processing to predict optical channel presence, channel power, signal to noise ratio and the quality (Q) factor parameter. With further processing, the bit error rate per channel can be estimated from the Q factor. The technique is realized on a system-on-a-chip CMOS technology which can potentially improve all optical networking architectures.
The information capacity of dense wavelength division multiplexing (DWDM) optical systems is reviewed. The effect of optical beat interference of closely spaced optical carriers sets the limit on the allowed channel spacing even in the absence of nonlinear effects. Present DWDM networks operating at 10.7 Gb/s in the C and L bands region have channel spacing no less than 25 GHz. We show that this limit is a constraint and smaller spacing may not be allowed without further optical and electrical pulse shaping.
A two dimensional acousto-optic cell array (AOCA) to be used as an optical MUX/DEMUX in DWDM systems has been analyzed. The diffraction efficiency, deflection angle and RF frequency required for the system have been determined.
The dependence of the mode partition noise (MPN) and the power penalty associated with it can be measured from the source spectral width. Our findings show that there is strong dependence of the carrier lifetime on the bit error rate degradation caused by MPN on the spectral width of the vertical cavity surface emitting laser (VCSEL). VCSELs with smaller spectral width (shorter carrier lifetime) exhibited smaller MPN induced power penalty. We found that the theoretical calculation of the power penalties caused by MPN from the carrier lifetime and the spectral width is in good agreement with the measured system penalties.
Polarization-mode-dispersion (PMD) tolerance of a duobinary modulation format is investigated. With the use of 2.5 Gb/s Mack Zehnder modulator for modulation and optical pulse shaping of a 64 channels (10.7 Gb/s) dense wavelength division multiplexing metro networks, the electrical filter needed in conventional duobinary is no longer needed. The proposed method cut down in the complexity and cost of the duobinary transceiver. This technique allows the use of 10 Gb/s MZ modulator for 40 Gb/s duobinary transmission. We also used electronic compensation to adaptively compensate for PMD/GVD.
Subcarrier Multiplexed (SCM) systems have received a considerable amount of interest, mainly in areas such as radioon-fiber systems and multi-channel video distribution. SCM systems, which use double sideband transmission, however experience high dispersion penalty especially in long distance transmission. Several techniques have been proposed to improve this, one of which is optical single sideband modulation. Recently, a tandem single sideband (TSSB) technique that enables transmission of different channels on each of the two sidebands was proposed. This effectively doubles the bandwidth efficiency while improving the dispersion penalty. In this paper, we demonstrate a novel technique to transmit and receive in the proposed TSSB technique using orthogonal carriers. Two channels of 200 Mb/s NRZ data were used to modulate a pair of orthogonal RF carriers and subsequently transmitted using the TSSB technique. Although the RF spectrum of the two received channels overlaps one another, they can be separated using quadrature demodulators. In this paper, we report simulation results of error free transmission for two 200 Mb/s channels using orthogonal carriers in TSSB systems.
Using Cyclic Transparent Optical Polymer (CYTOP), a perfluorinated graded index fiber, different transmission characteristics were investigated. Graded index perfluorinated fibers can support multi-Gb/s date rates form 0.83 um to 1.3 um. High bit rates can be obtained over 0.5 um wavelength range where optical transmitter and receivers technologies are already matured. A distributed feedback laser source at 1.3 um and a low cost InGaAs detector had been used in an error free transmission for both modulated multichannel transmission and directly modulated digital transmission for both modulated multichannel transmission and directly modulated digital transmission at 2 Gb/s. Two data channels at 145 Mb/s are mixed using binary phase shift keying BPSK modulation technique index of 5.3 percent. Also, the dispersion power penalty of the CYTOP fiber was measured and found to be less than 1 dB suggesting that the fiber induced distortion is small.
For short distance communications, graded index polymer optical fiber has been proposed as the physical transport layer for high data rate networks. This paper reports the results of various transmission experiments through polymer optical fiber. Bit-error-rate of < 10-9 has been obtained after transmission through 200 m of polymer optical fiber at received optical powers of -22 dBm at 155 Mb/s and -19 dBm at 622 Mb/s respectively. The experiment utilized a 659 nm laser as the source and a Si photodiode as a detector. The measured power penalty due to modal noise of < 1 dB is in agreement with the calculated results. The performance of a hybrid AM/BPSK optical fiber transmission system has been investigated. A BPSK modulated 2 Mb/s pseudorandom digital channel is substituted for one of the AM channels in a 60-channel cable TV system. For the subcarrier modulated digital channel, a bit error rate < 10-9 is obtained after transmission through 200 m of fiber. The intermodulation distortion (IMD) effects using long and short fiber lengths have been studied. The results show that distortion caused by the laser non-linearity did not degrade the system at low modulation depth. However, as the modulation depth of the BPSK signal is increased, the distortion is more pronounced. The differences in the measured IMD between the long and the short fiber is negligible, suggesting the fiber-induced distortion in the transmission system is small.
The high-speed modulation characteristics and performance in optical fiber transmission links of oxide confined vertical cavity surface emitting lasers are reported. The lasers have bandwidths of 13 GHz. Error-free transmission is obtained for both subcarriers modulated multichannel transmission and directly modulated digital transmission at 8 Gb/s.
This paper reports the result of transmission experiments through 200 m of plastic optical fiber at 155 Mb/s and 622 Mb/s. Bit-error-rates of < 10-9 has been obtained at received optical powers of -22 dBm at 155 Mb/s and -19 dBm at 622 Mb/s respectively. The measured power penalty due to model noise of < 1 dB is in agreement withthe calculated result.
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