• Journal of the Optical Society of Korea
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• v.7 no.4
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• pp.224-229
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• 2003

We report a novel optical delay line that can be implemented using only optical fiber and fiber devices without the need for any bulk-optic devices such as lens, prism, and moving mirror. The dispersive property of a chirped fiber Bragg grating (CFBG) is exploited to get the delay. The proposed delay line constitutes two identical CFBGs cascaded in the reverse order with one of them being strained. Analysis reveals that the small displacement or the strain applied on the CFBG is effectively amplified in the delay line by the ratio of the minimum resonant wavelength and the reflection bandwidth of the CFBG. The dispersion properties of the CFBG with and without the strain are analyzed in detail. The theoretical performance of the proposed delay line is also discussed. Applications of the proposed delay line are expected in the field of high-speed optical coherence tomograpy.

• Current Optics and Photonics
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• v.2 no.1
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• pp.34-38
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• 2018

An X-band microwave photonic (MWP) filter using switch-based fiber-optic delay lines has been proposed and experimentally demonstrated. It is composed of two electro-optic modulators (EOMs) and $2{\times}2$ optical MEMS-switch-based fiber-optic delay lines. By changing time-delay difference and coefficients of each wavelength signal by using fiber-optic delay lines and an electro-optic modulator, respectively, a bandpass filter or a notch filter can be implemented. For an X-band MWP filter with four channel elements, fiber-optic delay lines with the unit time-delay of 50 ps have been experimentally realized and the frequency responses corresponding to the time-delays has been measured. The measured frequency response error at center frequency and the time-delay difference error were 180 MHz at 10 GHz and 3.2 ps, respectively, when the fiber-optic delay line has the time-delay difference of 50 ps.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.12
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• pp.31-44
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• 1996

Since optical delay line signal processing which utilizes optical fiber as delay line elements can provide high speed and broadband signal processing, the optical delay line signal processing has numerous applications. Recently, many research papers which optical delay line signal processing techniques are being applied to OCDMA are published. The author has published paper on the design method for optical fiber filters of lattice structure. However, the previous design method does not realize the transfer function all the time. It can be realized with constraints. In this paper, we propose the design method that can realize the transfer function all the time without any constraints for the optical fiber filter of lattice structure.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.80-87
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• 1999

We propose a new recirculating fiber delay-line filter structure. In proposed system, we insert a fiber Bragg grating(FBG) into a recirculating fiber delay line and it operates as a partially reflection mirror. Therefore, the transfer function of the system is given by the recirculating delay output part and the multiple-reflected output part due to a FBG. By adjusting the parameters such as coupling coefficient, reflectivity of FBG, and gain, we can make the system operate in various filter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5B
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• pp.365-369
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• 2012

It is very important to control synchronization by inter-network delay compensation in high speed synchronous optcial transmission network systems. In this study we designed a delay measurement system based on OTDR using Rayleigh backscatterer in order to compensate for time delay due to the length of optical fiber line. We observed waveform variations on both averaging time and peak power of laser pulse. Finally, we executed experimental demonstration on its accuracy and test repeatability by comparison to the methods practically used in the industry. Experimental results show maximum error of 0.06usec and standard deviation of 0.021usec, which means it's possibly applied to delay control system for mobile repeaters and stations.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.4 no.1
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• pp.7-13
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• 2005

In this paper, we propose the time synchronization module on fiber optic repeater to use optic line delay for obtaining time synchronization between up-link and down-link, in the 2.3 GHz WiBro network using TDD/OFDM (Time Division Duplex/Orthogonal Frequency Division Multiplexing) Generally, when we use fiber optic repeater to remove the shade area, it occurs transmission delay which is caused by optic transmission between RAS (Radio Access Station) and fiber optic repeater and inner delay of fiber optic repeater. Because the WiBro system is adopting a TOO method and there exists the difference of switching time which is caused by these delay between up-link and down-link, it occurs ISI (Inter Symbol Interference), ICI (Inter Carrier Interference). These interference results in the reduction of the coverage. And the inconsistency between Up-Link and Down-Link switching time maybe gives rise to the interruption of communication. In order to prevent these cases, we propose synchronization module using analog optic line delay as the one of synchronizing up-link and down-link. And we propose the consideration factor for the designing time synchronization module and the feature of optic line of analog method. The measurement result of optic line time synchronization module of structure proposed is as follows, the delay error of $0.5{\mu}g$ and the insertion loss value below maximum 4.5dB in range of $0{\sim}40{\mu}s$. These results fully meet the specification of WiBro System.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.10
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• pp.95-102
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• 2003

The buffering is a promising solution to resolve the contention problem in optical network. we study the packet loss probability and the dimensioning of optical buffer using a Fiber Delay Line for variable length packet. In this paper, we study the relation between the granularity and the loss of FDL buffer in Single-Stage FDL buffer and propose the Single-Bundle Multi-Stage FDL buffer. The Multi-Stage FDL buffer is too early yet to apply to the current backbone network, considering the current technology in view of costs. but we assume that the above restriction will be resolved in these days. The appropriate number of delay and pass line for a dimensioning is based on a amount of occupied time by packets. Once more another multi-stage FDL buffer is proposed, Split-Bundle multi-stage FDL buffer. The Split-Bundle ms-FDL buffer is more feasible for a FDL buffer structure, considering not only a size of switching matrix but also a bulk of switching element. its feasibility will be demonstrated from a loss probability.

• Korean Journal of Optics and Photonics
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• v.18 no.4
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• pp.274-279
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• 2007

We fabricated and characterized an optical delay line for optical coherence tomography (OCT). The delay line was composed of a cylindrical piezoelectric transduce (PZT) and a single mode optical fiber. The OCT system used a duplex scanning optical delay line which was symmetrically driven in the reference and sample arms. We showed that the sinusoidal-wave was superior to a triangular-wave for driving the optical delay line for scanning depth and repeatability.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.159-164
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• 2006

We demonstrate a compact optical coherence tomography(OCT) system based on the optical fiber delay line controlled by a cylindrical piezo-electric transducer(PZT). An 18-m length of single mode fiber is wrapped under constant tension around a PZT. Approximately 134 windings are used. Wraps of the long length of fiber allow the small expansion of the PZT to be magnified to an optical path length delay of 0.78 m. The OCT system shows characteristics for 2-dimensional imaging, exhibiting 96.9dB of signal-to-noise ratio(SNR), $18.6{\pm}0.5\;{\mu}m$ of axial resolution, and $5\;{\mu}m$ of lateral resolution with samples.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1707-1713
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• 2000

We have proposed a tunable optical ADM using a fiber-optic transversal filter which is composed of fiber couplers and metal-film coated fiber-optic tapped delay-lines with a flat spectral response in abroad range of wavelength. Simulation results show that the optical loss at the DROP and PASS wavelengths of the OADM is negligible and the wavelength tunability is 0.78${\mu}{\textrm}{m}$/ps for the unit time delay of 2 ps. In order to investigate the effects of wavelength drift of the imput optical signal on the OADM the loss at the DROP port and the crosstalks to the other ports have been calculated. The maximum bit rates have been calculated at 46.26 Gb/s for the input Gaussian pulse width of 10 ps.