• Journal of the Optical Society of Korea
• /
• 제12권4호
• /
• pp.326-336
• /
• 2008

A WDM-PON has been considered as an ultimate solution for access networks. However, there were many technical and practical issues for commercial deployment. These issues were solved with wavelength locked F-P LD and the WDM-PONs employing this optical source were commercialized. These WDM-PON systems have been deployed in Korea, Europe, and US. We reviewed wavelength locking technology and WDM-PON achievements. When we inject spectrum sliced broadband light into an F-P LD, the multimode output is changed to a quasi single mode. Then, we can use the single mode light for WDM signal transmission. The broad spectral gain of the semiconductor gain medium enables a color-free operation of WDM-PON, i.e., an identical ONT can be used for each user. The wavelength locking properties depend on many parameters, especially alignment of injection wavelength to a lasing mode, passband profile of AWG and front facet reflectivity of F-P LD. However, these dependencies can be reduced by proper design of the laser and the injection bandwidth. Thus, WDM-PON systems have been achieved with color-free operation.

• 조명전기설비학회논문지
• /
• 제27권8호
• /
• pp.75-82
• /
• 2013

We propose a fiber grating sensor system for condition monitoring of large scale wind turbine blades. For the feasibility test of the proposed sensor system, a down-scaled wind turbine has been constructed and experimented. Fiber grating sensors were attached on a blade surface for distributed strain and temperature measurements. An optical rotary joint was used to transmit optical signals between the FBG sensor array and the signal processing unit. Instead of broadband light source, we used a wavelength-swept fiber laser to obtain high output power density. A spectrometer demodulation is used to alleviate the nonlinear wavelength tuning problem of the laser source. With the proposed sensor system we could measure dynamic strain and temperature profiles at multi-positions of rotating wind turbine blades.

• Journal of the Optical Society of Korea
• /
• 제17권4호
• /
• pp.312-316
• /
• 2013

A novel fiber-optic sensor system is suggested in which fiber Bragg grating sensors are demodulated by a wavelength-sweeping fiber laser source and a spectrometer. The spectrometer consists of a diffraction grating and a 512-pixel photo-diode array. The reflected Bragg wavelength information is transformed into spatial intensity distribution on the photo-diode array. The peak locations linearly correspond to the Bragg wavelengths, regardless of the nonlinearities in the wavelength tuning mechanism of the fiber laser. The high power density of the fiber laser enables obtaining high signal-to-noise ratio outputs. The improved demodulation characteristics were experimentally demonstrated with a fiber Bragg grating sensor array with 5 gratings. The sensor outputs were in much more linear fashion compared with the conventional tunable band-pass filter demodulation. Also it showed advantages in signal processing, due to the high level of photo-diode array signals, over the broadband light source system, especially in measurement of fast varying dynamic physical quantities.

• 한국광학회지
• /
• 제23권6호
• /
• pp.264-268
• /
• 2012

본 논문에서는 파장분할 다중방식의 수동형 광 가입자망(WDM-PON: Wavelength Division Multiplexing - Passive Optical Network)에서 매우 구조가 간단하고 저비용으로 구현 가능한 방송신호 전송 방법을 제안한다. 이는 하나의 광대역 증폭된 자발 광원(Amplified Spontaneous Emission: ASE)과 편광 독립 반사형 반도체 광 증폭기(Polarization Independent-Reflective Semiconductor Optical Amplifier: PI-RSOA) 만으로 구현이 가능하기 때문이다. 채널당 1.25 Gb/s 속도에서 24개의 가입자 채널에 대해 30 Km 이상의 방송 신호 전송 시, 무오류(error-free) 성능을 갖는 것을 실험적으로 증명하였다.

• 전자공학회논문지SC
• /
• 제45권1호
• /
• pp.25-30
• /
• 2008

본 논문에서는 상용 고휘도 백색광 LED 및 CCD 어레이 검파기를 이용하여 Fourier-domain 방식의 광 계측기를 구현하였다. 제안된 기술의 축 방향 측정 거리 범위는 $125{\mu}m$이고, 축 방향 분해능은 $1.24{\mu}m$이다. 기존 시스템이 고가의 광대역 광원을 사용하면서도 분해능이 수 ${\mu}m$ 이상인 것에 비추어 볼 때, 본 시스템은 저가의 상용 LED와 CCD 어레이 검파기를 사용하여 구현되므로 소형이며 가격적인 면에서 유리하면서도 높은 분해능을 얻을 수 있다.

• 한국광학회지
• /
• 제8권3호
• /
• pp.183-188
• /
• 1997

색분리 필터는 하나의 파장영역에서는 고반사, 다른 파장영역에서는 고투과를 제공하는 광학소자이다. 레이저를 이용한 디스플레이장치의 광학계를 구성하기 위해서는 정확한 색상의 분리가 요구되며, 광학계 효율 측면에서 매우 중요하다. 본 연구에서는 Kr-Ar laser(혼합 gas)빔을 R.G.B 삼색으로 분리하여 화상을 구현하기 위한 미러와 필터를 아래와 같은 특성을 만족하도록 설계 및 제작하였고, 그 특성은 45.deg./S-편광된 빔을 입사시켜서 1) R(반사율)>99% 450~493 nm, T(투과율)>90% 509~685 nm 2) R(반사율)>99% 509~685 nm, T(투과율)>90% 450~493 nm 3) R(반사율)>99% 509-585 nm, T(투과율)>90% 600~683 nm를 각각 만족하는 소자로 색분리를 실현하여 레이저 프로젝션 시스템을 구성하는데 사용하였다.

• ETRI Journal
• /
• 제23권1호
• /
• pp.1-8
• /
• 2001

The performance of a long wavelength-band erbium-doped fiber amplifier (L-band EDFA) using 1530nm-band pumping has been studied. A 1530nm-band pump source is built using a tunable light source and two C-band EDFAs in cascaded configuration, which is able to deliver a maximum output power of 23dBm. Gain coefficient and noise figure (NF) of the L-band EDFA are measured for pump wavelengths between 1530nm and 1560nm. The gain coefficient with a 1545nm pump is more than twice as large as with a 1480nm pump. It indicates that the L-band EDFA consumes low power. The noise figure of 1530nm pump is 6.36dB at worst, which is 0.75dB higher than that of 1480nm pumped EDFA. The optimum pump wavelength range to obtain high gain and low NF in the 1530nm band appears to be between 1530nm and 1540nm. Gain spectra as a function of a pump wavelength have bandwidth of more than 10nm so that a broadband pump source can be used as 1530nm-band pump. The L-band EDFA is also tested for WDM signals. Flat Gain bandwidth is 32nm from 1571.5 to 1603.5nm within 1dB excursion at input signal of -10dBm/ch. These results demonstrate that 1530nm-band pump can be used as a new efficient pump source for L-band EDFAs.

• 한국음향학회지
• /
• 제23권1호
• /
• pp.8-16
• /
• 2004

천해환경에서 저주파 광대역신호와 수직선배열을 이용하여, 퇴적층의 지음향인자(층두께, 종파속도, 종파감쇠계수, 밀도)를 역추정하였다. 역산방법은 모델 기반의 역산으로 유전알고리즘 (Genetic Algorithm)을 이용한 일관적 광대역 정합장처리(Coherent Broadband Matched Field Processing)기법을 사용하였다. 저주파 광대역음원으로 사용된 상업용 전구의 내폭신 호는 짧은 시간동안 많은 변화를 포함하는 천이신호이기 때문에, 분석시 시간과 주파수에 따른 창함수의 조절이 요구되는데, 주기신호분석에 주로 사용되는 퓨리에 기반의 분석방법은 이러한 점에서 많은 어려움이 있다. 본 논문에서는 해양도파관에서 근거리 음파전달 시 계측된 시계열신호로부터 다중경로성분을 구분하고 추출하기 위하여 시간-주파수영역에서 창함수의 크기조절이 가능한 웨이블릿 변환을 통한 신호 분석을 수행하였고, 분석된 실측음장과 계산된 복제음장의 연속웨이블릿 계수를 상호상관 시킴으로써 비용함수를 정의하였다. 비용함수의 전역최고점을 찾는 최적화 과정을 통하여 각 퇴적층의 지음향인자들을 역추정하였다. 특히 역산인자의 민감도에 따른 퇴적층별, 인자별, 분리연산을 수행함으로써 최적화과정에서 참값으로의 수렴효율을 높였다. 역산의 결과 실험해역 퇴적물 상층부에는 두께 44.43m, 음속 1549 m/s의 모래-실트-점토질(sand-silt-clay)층이 존재하고, 그 하부에는 12.28m 음속 1993 m/s의 거친모래질(Coarse sand)층의 존재를 추정해 내었다. 또한 역산 결과를 시추자료 및 탄성파 자료와 비교함으로써 본 논문에서 제안한 역산 방법의 유효성을 확인하였다.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
• /
• pp.31-34
• /
• 2002

A study on the method that can measure the internal strain of composite materials is performed to monitor the health status of composite structures. A fiber optic sensor was constructed using the total reflected extrinsic Fabry-Perot interferometer(TR-EFPI) probe with a broadband light source. Result obtained from electrical strain gage adhered on the aluminum beam specimen was compared with that from the fiber optic TR-EFPI sensor and showed a good agreement. It was found that fiber optic TR-EFPI sensor system was adequate for monitoring the strain and thus failure processes in the interior of composite materials.

• Journal of the Optical Society of Korea
• /
• 제18권6호
• /
• pp.646-649
• /
• 2014

Performances of spectrum-sliced channels are strongly affected by their relative intensity noise (RIN). We use polarization-independent optical modulators (PIOMs) for spectrum-sliced channels to suppress their RIN. The PIOM driven by a high sinusoidal voltage signal evenly redistributes optical frequency components in the spectral domain and reduces the RIN. It can be used at a broadband light source (BLS) output to produce spectrum-sliced channels having lower RIN values. Also, it can be used for each spectrum-sliced channel within each optical network unit (ONU). In our experiment, where 12.5-GHz-spaced spectrum-sliced channels are used in 1-GbE speed, the use of PIOM at the BLS output reduces the bit error rate (BER) of the spectrum-sliced channel by more than an order of magnitude. The use of PIOM within the ONU reduces the BER by approximately 3 orders of magnitude.