• ETRI Journal
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• v.28 no.2
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• pp.257-259
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• 2006

In this letter, we will evaluate the performance degradation of a 40 km high-speed (40 Gb/s) optical system, induced by optical fiber variations of the chromatic dispersion induced by temperature changes. The chromatic dispersion temperature sensitivity will be estimated based on the signal quality parameters.

• ETRI Journal
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• v.37 no.6
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• pp.1120-1128
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• 2015

We propose a pseudo optical N-level pulse-amplitude modulation (PO PAM-N) signal using a few externally-modulated lasers (EMLs) operating at different wavelengths, which is suitable for upgrading the transmission speed over an optical link of < 10 km single-mode fiber with low-cost components. To compare a PO PAM-N signal with that of a standard optical PAM-N signal, we perform experiments for evaluating the performance of a 51.56-Gb/s PO PAM-4 signal and standard 51.56-Gb/s optical PAM-4 signal. The receiver sensitivity (at $BER=10^{-5}$) of the PO PAM-4 signal is 1.5 dB better than the receiver sensitivity of a standard optical PAM-4 signal. We also investigate the feasibility of PO PAM-N (N = 4, 8, and 16) signals operating at 103.12 Gb/s, considering relative intensity noise, timing jitter, extinction ratio (ER) of EMLs, and dispersion. From the results, a PO PAM-8 signal performs better than PO PAM-4 and PO PAM-16 signals at 103.12 Gb/s. Finally, we suggest a timing control method to suppress the effect of dispersion in a PO PAM-N signal. We show that the tolerance to dispersion of a 103.12-Gb/s PO PAM-8 signal can be improved to ${\pm}40ps/nm$ by applying a proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1B
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• pp.105-111
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• 2000

To realize a desired characteristics of an optical transversal fitters, The number of optical amplifiers as same as the lentgh of a given transfer function is needed In this paper, we consider an optical transversal filter that uses only one fiber amplifier, which can realize a constant(=$\alpha$) times of a given transfer function with e as large as possible in order to make use of optical signal energy. We also present some applications using this optical fiber filter.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.322-325
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• 1999

We report fiber guiding experiments on the Photonic Quantum Ring(PQR) laser diode. In the 1km transmission measurements, we find that the PQR performs much better than the VCSEL. This suggests that the PQR laser is very promising candidate for LAN-range optical data communications. On the other hand, we have also fabricated 8$\times$8 PQR laser arrays and measured spatial decays for free space properties without using any guiding optics, which showed about 1m distance of spectral angle sensing.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.1
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• pp.67-74
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• 2009

In this paper, we investigate the performance limitations of SubCarrier Multiplexed(SCM) WDM systems using optical Double-Side Band(DSB) modulated 16 QAM signals. The Bit-Error Rate(BER) performance is evaluated under various optical transmission links including the effects of the dispersion and fiber nonlinearities such as SPM(Self-Phase Modulation) and XPM(cross-phase modulation). After simulation of SCM-WDM systems, the dominant factors determining the entire system performance are appeared to be the nonlinearity of MZ(Mach-Zehnder) modulator and the SCM channel spacing. The BER performance of subcarrier channels in the higher frequencies was degraded with the large dispersion effect only, however, the performance was improved a little with a combined effect of fiber dispersion and nonlinear effect when the hish fiber launching power was applied.

• Journal of Communications and Networks
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• v.10 no.1
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• pp.1-4
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• 2008

This paper reports the design of a multiwavelength fiber laser source that utilizes a linear cavity of hybrid Brillouin/Erbium fiber laser (BEFL). The output power, threshold power and free running cavity modes were investigated against the pump powers. The structure exhibited low threshold operation of 4 mW at 2.3 mW injected Brillouin pump power. The optimization of Brillouin pump wavelength, power and Erbium gain led to a maximum possible number of channels generated. Simultaneous and stable operation of 21 channels with 10.88 GHz channels spacing were obtained from this architecture at 1 mW injected Brillouin pump power and 90 m W Erbium doped fiber pump power in the 1555 nm region.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.5
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• pp.395-402
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• 1991

Submarine Optical Fiber Cable Link becomes a major transmission madi a in many countries and Continents thanks to development of low attenuation fiber and its capability of carryung broadband data. United States of America and Japan are aggressively planning to construct international submarine optical fiber links in North-East Asia. But the links do not connect Korea and Korea becomes isolated in the international communication network. This paper shows a strategy on submarine optical fibre cable links that make Korea a HUB station in North East As a without heavy investment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.12
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• pp.3277-3285
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• 1996

In this paper, w designed an opical power distribution device for application to an optical switching and an optical subscriber loop. We fabricated PSG thin film by LPCVD. Based on the measured index of fabricted thin film, rib-type waveguide was transformed to two-dimension by the effective index method and we simulated dispersion property to find asingle-mode condition. We found that the optimum design parameters of rib-type waveguide are:cladding layer of 3.mu.m, core layer of 3.mu.m, buffer layer of 10.mu.m, and core width of 4.mu.m. Each side of the guiding region was etched down to 4.mu.m to shape the core. We used these optimum parameters of the rib-type waveguide with branching angle of 0.5.deg. and simulted the Y-branch waveguide by the BPM simulation. Numerical loss in branching area was claculated to be 0.1581dB and equal to the total loss of the Y-branch. The loss of the fabricated Y-branch waveguide on PSG film ws 1.6dB at .lambda.=1.3.mu.m before annealing but was 1.2dB after annealing at 1000.deg. C for 10 minutes. Consequently, the loss of branching area from 3000.mu.m to 6000.mu.m in the z-direction was 0.8dB, and single-mode propagation was confirmed by measuring the near field pattern. For coupling the fabricated Y-branch waveguide with an optical fiber, we fabricated V-groove which was used as the upholder of optical fiber. An etching angle was 54.deg. and the width and depth of guiding groove was 150.mu.m, 70.mu.m, respectively. The optical fiber is inserted onto V-groove. Both the Y-branch and V-groove were connected through the index matching oil. Coupling loss after connecting Y-branch and the optical fiber on V-groove was 0.34dB and that after injecting index mateching oil was 0.14dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3A
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• pp.153-159
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• 2005

In this paper, we propose All-Optical WDM Buffer System for resolving the contention of Packets in Optical Packet Switching System. The proposed system consists of tunable wavelength converters based on SOA, N×N AWG, and fiber delay lines. This structure can reduce ASE and cross-talk noise because the contending packets are sent and buffered through each different path determined by a wavelength routing. We also performed buffering experiment for two contending WDM optical pulses with each 50ns width, and found that the contending problem is resolved well.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5A
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• pp.323-332
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• 2003

We have proposed and implemented a novel cost-effective optical subcarrier mutiplexing transceiver for base station without light sources in which optical signal can be transmitted bidirectionally over a single optical fiber. Modulated optical signal is retransmitted from the base station to the central office using a ring-type base station which consists of a circulator and an Mach-Zehnder modulator, where the optical source is supplied from the central office. In order to investigate the feasibility of the proposed base station without light sources, we have measured adjacent channel power ratio and carrier to noise ratio by transmitting the IS-95 CDMA signal and 14 tones carrier signal bidirectionally through the system.