• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.731-741
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• 2009

Optical repeater is often installed at the isolated area. Spatial separation makes it possible to reduce the inter-code interference when secondary scrambling codes are used for traffic connected through repeater. In this paper, we propose five secondary scrambling code usage scenarios with the aids of optical repeater to maximize the user capacity. In order to evaluate the performance, dynamic system level simulation is performed. We also propose a base station-repeater switching where each active users can change access points by comparing the channel condition from base station and repeater thorough secondary common pilot channel (S-CPICH) signal to noise-interference ratio (SINR). Moreover, primary-secondary scramble code replacing scheme is proposed which replaces secondary scramble code with primary scramble code when a call using primary scramble code is ended and its corresponding OVSF code is available to users using the secondary scramble code

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8C
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• pp.1086-1103
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• 2004

Most research efforts on the OCDMA technology assume single-bit-per-symbol transmission techniques such as on-off keying. However, achieving high spectral efficiency with such transmission techniques is likely to be a challenging task due to the "unipolar" nature of optical signals. In this paper, an M-ary transmission technique using more than two equally-weighted codes is proposed for OCDMA local area networks, and ie BER performance and spectral efficiency are analyzed. Poison frame arrival and randomly generated codes are assumed for the BER analysis, and the probability of incorrect symbol detection is analytically derived. From the approximation, it is found that there exists an optimal code weight that minimizes the BER, and its physical interpretation is drawn in an intuitive and simple statement. Under the assumption of this optimized code weight and sufficiently large code dimension, it is also shown that the spectral efficiency of OCDMA networks can be significantly improved by increasing the number (M) of symbols used. Since the cost of OCDMA transceivers is expected to increase with the code dimension, we finally provide a guideline to determine the optimal number of symbols for a given code dimension and traffic load.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.4
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• pp.27-32
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• 2014

Two-dimensional hybrid codewords are generated by using each row of identity matrix for spatial encoding and nonideal symmetric balance incomplete block design(BIBD) code for spectral encoding. This spatial/spectral optical code-division multiple-access (OCDMA) network uses single-balanced detectors to abstract the desired information bits and to eliminate the multiple-access interference(MAI). Analytical results show that the number of simultaneous users increases significantly by using the proposed hybrid codes.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.1
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• pp.30-34
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• 2005

This study shows the lasing characteristics of InGaAs/InGaAsP multiple-quantum-well waveguide-type depleted optical thyristor (DOT) using the vertical window. The measured switching voltage and current are 3.36 V and 10 ㎂, respectively. The lasing threshold current is 131 mA at 25 ℃. The output peak wavelength is 1570 nm at a bias current of 1.22 Ith and there is not input signal anymore in the output port. The vertical injection depleted optical thyristor - laser diode (VIDOT-LD) using the vertical-injection structure shows very good isolation between input and output signal.

• Journal of the Optical Society of Korea
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• v.14 no.1
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• pp.28-32
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• 2010

We demonstrate binary spectral phase coded waveform discrimination at 10 GHz for narrow band optical code-division multiple-access (NB-OCDMA) via direct electrical detection without using any optical hard-limiter. Only 9 phase-locked, 10 GHz spaced, spectral lines within a 100 GHz spectral window are used for the phase coding. Considerably high contrast ratio of 5 between signal and multiuser access interference noise can be achieved for $4{\times}10\;G\;pulse/sec$ timing coordinated OCDMA at a simple electrical receiver with 50 GHz bandwidth.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.142-146
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• 2012

Today, the demand for high-speed data communication and mobile communication has exploded. Thus, there is a growing need for optical communication systems that convert large volumes of data to optical signals and that accommodate and transmit the signals across long distances. Digital optical communication with these characteristics consists of a master unit (MU) and a slave unit (SU). However, the digital optical units that are currently commercialized or being developed transmit data without compression. Thus, digital optical communication using these units is restricted by the quantity of optical frames when adding diversity or operating with various combinations of CDMA, WCDMA, WiBro, GSM, LTE, and other mobile communication technologies. This paper suggests the application of a data compression algorithm to a digital signal processor (DSP) chip as a field programmable gate array (FPGA) and a complex programmable logic device (CPLD) of a digital optical unit to add separate optical waves or to transmit complex data without specific changes in design of the optical frame.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.1
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• pp.53-59
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• 2000

We propose a modified nonlinear fiber optic interferometer which can serve to generate binary optical pulse sequences for CDMA networks, and to decode them. In one arm cross-phase modulation between a CW signal and a counter- or copropagating high-power pulse takes place in sequences of segment connected via VDM couplers. Preliminary experimental results on code generation as well as autocorrelation and crosscorrelation are presented, using Sagnac interferometer. As we expected, the experimental results show that the outputs of the interferometer device are not summed simply on the basis of power, but the sin-squared version of it. Arbitrary codes can in principle be implemented.

• ETRI Journal
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• v.26 no.1
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• pp.13-20
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• 2004

We propose a new optical code division multiple access (OCDMA) scheme for reducing multiple access interference (MAI) and enhancing performance for optical subscriber access networks using modified pseudorandom noise (PN)-coded fiber Bragg gratings with bipolar OCDMA decoders. Through the bipolar OCDMA decoder and the modified PN codes, MAI among users is effectively depressed. As the data are encoded either by a unipolar signature sequence of the modified PN code or its complement according to whether the data bit is 1 or 0, the bit error ratio (BER) can be more improved with the same signal to interference plus noise ratio over the conventional on-off shift keying-based OCDMA system. We prove by numerical analysis that the BER of the proposed bipolar OCDMA system is better than the conventional unipolar OCDMA system. We also analyze the spectral power distortion effects of the broadband light source.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.39-43
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• 2001

A system, IS-95C coupler that combines the signals of IS-95A/B and IS-95C BTS and compensates the differences between the signals of two systems and connected to optical repeater If no IS-95C coupler exist, Optical repeater can't service of signal balanced. A system carries on combination, amplification, level modulation function of the TX signals(IS-95A/B & IS-95C) and division and level modulation function of the RX signals. Isolation satisfied above 100dB.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.5
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• pp.121-127
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• 2013

When input power is small, nonideal symmetric balance incomplete block design(BIBD) code design is effective in the spectral-amplitude-code(SAC) optical code-division multiple-access (OCDMA) system. But the number of simultaneous users is not sufficient. To overcome this property, we propose 2-D BIBD codes, where nonideal BIBD codes are used as spectral code and ideal BIBD codes are used as spatial codes. Analytical results show that the number of simultaneous users increases significantly.