• Journal of Digital Convergence
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• v.10 no.4
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• pp.265-270
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• 2012

The subscriber access network is cause of the bottleneck phenomenon because equipment and infrastructure were not originally designed for busty high-bandwidth traffic between MAN(Metro Area Network) and LAN(Local Area Network). Whether riding on shorter copper drops or optical fiber, Ethernet is emerging as the future broadband protocol of choice, offering plug and play simplicity, and low cost. EPON(Ethernet Passive Optical Network) combines point-to-multipoint optical infrastructure with low-cost high-bandwidth Ethernet. The future broadband access network will be a combination of point-to-point and point-to-multipoint Ethernet, optimized for transporting IP data, as well as time critical voice and video. EPON is being considered as a novel communications infrastructure for next-generation broadband access network for the convergence of low-cost Ethernet equipment and low-cost fiber infrastructure. But, EPON has a problem with duplex multimedia services. It is the insufficiency of bandwidth for upstream. Because all ONUs use a shared transmission media for upstream. In this paper, we addressed the problem of upstream bandwidth in EPONs. We presented a wavelength division EPON supporting QoS in the differentiated services framework.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.1
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• pp.197-203
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• 2013

Optical power optimization of 10 Gbps 40 wavelength division multiplexing channels was analyzed at the 3000 km long-haul transmission distance when the link span distance was changed between 40 km and 140 km. The signal performance of the transmission was obtained as a Q value and it was compared when input power into SSMF and input power into DCF on the transmission link were changed. The optimized input power into SSMF increased linearly to link span distance with 1 dB/km. The optimized power into DCF increased linearly with 0.5 dB/km up to 100 km link span, but it had no variation at longer link span than 100 km.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.6
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• pp.612-620
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• 1987

In this paper, the optical modem for data link realization is designed with the advantages of optical fiber, large bandwidth, high speed and long haul communication. Modem interface, CCITT V.24 and EIA RS-232C is adopted for the compatibility with existing systems, and biphase coding format is used for digital modulation. And also, modem has serveral loopback test facility in order to diagnose system itself. Optical transmitter and receiver are designed to have the receiving sensitivity of -30dBm at $10^-9$BER in the short wavelength region. Developed system is capable of transmitting data rate at 1200bps up to 57.6Kbps in sync., and at any bps within DC to 200Kbps in async transmission.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1B
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• pp.31-41
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• 2000

It has been known that the optical code division multiple access (OCDMA) is a prominent future technology to support many simultaneous users and to increase transmission capacity of optical fiber. In this paper, we proposed the new construction of 2 dimensional code, which can be used as a codeword in temporal/wavelength OCDMA networks. New code family is obtained by extending the concept of Hamming correlation. All optical encoder and decoder for newly proposed code were also developed. In considering bit error ratio, we verified that new coding scheme outperforms conventional coding scheme by simulation. This system is applicable to asynchronous fast local area network, which needs a high security level and a flexible network configuration.

• ETRI Journal
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• v.13 no.4
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• pp.70-79
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• 1991

$In_1-x$$GA_X$$As_y$$P_1-y$ has a very wide range of applications in optoelectronic devices especially for optical communications because $In_1-x$$GA_X$$As_y$$P_1-y$ has the bandgap of the lowest dispersion ($1.3\mum$) and the lowest loss ( $1.55\mum$) of the optical fiber by changing the composition. The quality of $In_1-x$$GA_X$$As_y$$P_1-y$ epitaxial layer is believed to have a significant effect on the performance of device. The OMVPE growth conditions for the latticematched $In_1x$$GA_X$$As_y$$P_1-y$/InP were investigated. Effects of growth conditions such as V/III ratio, growth temperature, and Ga source material on the electrical and optical properties were studied. The composition, electrical and optical properities of $In_1-x$$GA_X$$As_y$$P_1-y$ were characterized using double crystal X-ray diffractometer (DCD), photoluminescence (PL), XPS(ESCA) and Hall measurement.

• Korean Journal of Optics and Photonics
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• v.22 no.4
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• pp.191-197
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• 2011

In this paper, we have designed an integrated triplexer which is the basic component for a FTTH(Fiber To The Home) system which can transmit CATV and voice/data at the same time in a single fiber. The integrated triplexer can be fabricated with a novel technique of "Micro-Block Stacking (MBS)" method which automatically aligns the optical components in the optical beam pass using accurate ceramic holders. We analyze the displacement of the optical focus according to the tolerances of the component dimensions and the assembly process using code V simulator. For the transmitter, the most serious shift of the focal points is caused by the displacements of the LD spot. So the focal point moves up to $72{\mu}m$ from the center point for ${\pm}25{\mu}m$, ${\pm}25{\mu}m$, ${\pm}30{\mu}m$ displacements. For the receiver the most serious shift of the focal points is caused by the displacements of a 0.8mm ball lens (for the analog receiving part) and a micro ball lens (for the digital receiving part), and the focal point moves up to $55{\mu}$ for ${\pm}55{\mu}m$, ${\pm}5{\mu}m$, ${\pm}55{\mu}m$ micro ball lens displacements.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.5
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• pp.571-577
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• 1989

In this paper, the double-refractive index profile, which is generalized a trapezoidal index profile, is proposed to study the characteristics of a optical fiber in the wave length 1.55um. Being compared with a triangle profile, it has many advantages over an optimum core radius, the minimum refractive index difference and the change of chromati dispersion characteristics with wavelength. Though the value of a varies from 2 to infinite, the same results are approximately obtained. Therefore, in fabrication of a fiber, the step part of trapezoidal index profile can replace the profile of a-power refractive index. Because the refractive index presented in this paper varies with a, it can be applied to multiple cladding fiber or segmented core fiber. And it is expected that the characteristics of the fiber are obtained.

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.327-332
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• 1997

We fabricated the high speed 1.55${\mu}{\textrm}{m}$ distributed feedback laser diodes (DFB-LD) using both two-step mesa etching process and semi-insulating InP current blocking layers. The devices characteristics were threshold current of ~15mA, slope efficiency of ~0.13mW/mA, and dynamic resistance of ~6.0Ω, with as-cleaved facets. The fabricated DFB-LD showed the single longitudinal mode with more than 40dB up to 6 $I_{th}$(CW condition), emitting at the wavelength of 0.546${\mu}{\textrm}{m}$. The -3dB bandwidth was >10㎓ at the driving current of 27mA, and the maximum -3dB bandwidth was ~18㎓ at 90 mA current, showing the superior frequency response of SI-PBH DFB-LD. In the 10Gb/s transmission experiment for 1.55${\mu}{\textrm}{m}$ DFB-LD module, maximum 10 km of single mode fiber(SMF) or 80 km of dispersion shifted fiber (DSF) could be transmitted with error free.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8A
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• pp.697-704
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• 2005

In this paper, Passive Temperature Compensation Technology is apply to 8-channel Optical multiplexer with 1000Hz channel spacing. The 8-channel multiplexer is fabricated by connecting three cascaded Mach Zehnder Interferometer(MZI) of optical fiber type, and each interferometer has the wavelength interval of 100GHz, 2000Hz and 4000Hz, respectively. Furthermore, to acquire uniform insertion loss, it is fabricated by using Wavelength Flatten Coupler(WFC) in which the variation of insertion loss is low. $CO_2$ laser to adjust precisely the wavelength. The optical fiber is very sensitive in the thermal variation around. Thus, When fabrication the prototype, it is applied a technique to compensate the optical thermal effect because the center wavelength at the output is shifted according to the thermal variation around. In summary, The prototype composed by eight cascaded MZI has an insertion loss of 5.5 dB, the bandwidth of 0.8nm at 0.5 dB point, and channel crosstalk of 25 dB. Furthermore, the loss dependent on polarization is measured as 0.06dB. Consequently, the output wavelength is shifted within 0.05 m when the surrounding temperature varies until $60^{\circ}C$

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.10
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• pp.2466-2472
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• 2013

Post-dispersion compensation methods for the 3000 km long-haul transmission distance using 10 Gbps 40 wavelength division multiplexing channels were analyzed and compared. First, each channel was compensated by an individual dispersion value, next each group of eight channels by an individual value, and lastly all forty channels by a single value. Considering the lower and highest performance channels and their values, the post-dispersion compensation method by each channel group showed the possibility to simplify the transmission system without sacrifice of signal performance.