• 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 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 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.

• 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.

• Korean Journal of Optics and Photonics
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• v.5 no.4
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• pp.493-498
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• 1994

A fiber-optic matched filter with Cr/ Au film-deposited fiber-optic delay lines is fabricated for a possible application as photonic packet address detectors for an all-optical slotted ring network. Correlation waveforms for a set of 6-bit address codes with 2.5 Gb/s are produced by simulation. It is shown that the measured correlation outputs agree well with the calculated ones.d ones.

• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.162-166
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• 2007

In this paper, we propose a WDM optical true time-delay (OTTD) beam former for phased way antenna (PAA) systems. It is composed of a delay lines matrix and a multiwavelength source with discrete DFB laser diodes. The building block of a delay lines matrix is a $2\times2$ optical MEMS switch with proper fiber-optic delay line connected between cross ports. A $4\times3$ matrix using four DFB lasers has been fabricated with unit time-delay difference of 12 ps. Maximum time-delay error was measured to be -1.74 ps and +1.14 ps at a radiation angle of $46.05^{\circ}$, corresponding to error range of $-2.87^{\circ}\sim+1.88^{\circ}$. By measuring time-delays at six different RF frequencies from 5- to 10-GHz, we verified the true time-delay characteristic of our OTTD.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.2
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• pp.213-217
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• 2015

Microwave Photonic(MWP) filters capable of use a bandpass filter or a notch filter with large bandwidth have been proposed. 4-lines${\times}$2-bit fiber-optic delay lines with a unit time-delay difference of 50 ps were experimentally realized. By changing the time-delay difference and the coefficients of microwave-modulated optical signals, the bandpass and notch filters were implemented and characterized.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.18-19
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• 2000

In this paper, packet error rates of an all-optical packet switching node, which uses a fiber-optic delay-line matched filter as the optical packet header processor, has been calculated for the various optical pulse shapes.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.58-59
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• 2002

Jitter noise power at the all optical packet header processor, which uses a fiber-optic delay-line matched filter, has been calculated for various optical pulse shapes.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.385-390
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• 2004

In this paper, we designed a 4-bit optical true time-delay(TTD) for phased array antennas(PAAs), which is composed of a wavelength-fixed optical source, 2 ${\times}$ 2 optical MEMS switches, and fiber-optic delay lines. A 4-bit TTD with a unit time delay difference of 6 ps for 10-GHz PAAs has been implemented. Measurement results on time delay show an error of -0.4 ps at maximum, corresponding to a radiation angle error of less than 1.63$^{\circ}$. Thus, the TTD implemented in this research performs in excellent agreement with theory. Each TTD line, composed of MEMS switches and fiber-optic delay lines, connected to the corresponding antenna element has insertion loss in between 1.36 ㏈ and 2.40 ㏈ depending upon the setup of the switches. On the other hand, the insertion loss difference between TTD lines was 0.32 ㏈ at maximum for a fixed radiation angle. The TTD structure proposed in this paper might be more reliable and economical than those previously proposed using tunable wavelength sources if proper power equalization either with gain control of RF amplifiers or variable attenuators is achieved.