Current Optics and Photonics
Vol. 6, No.3(Jun. 2022)
한국광학회지
Vol. 33, No.3(Jun. 2022)
K-Light
Vol5, No.3(Jul. 2022)
한국광학회 공식 SNS 계정 바로가기
트위터
인스타그램
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[Editor's Pick] Current Optics and Photonics Vol. 6 no. 3 (2022 June)
Spectral Reconstruction for High Spectral Resolution in a Static Modulated Fourier-transform Spectrometer
Ju Yong Cho1, Seunghoon Lee2, Hyoungjin Kim1, and Won Kweon Jang1*
Current Optics and Photonics Vol. 6 No. 3 (2022 June) pp. 244-251
DOI: https://doi.org/10.3807/COPP.2022.6.3.244
Fig. 1 The static modulated Fourier-transform spectrometer during the reconstruction process and a magnified optical layout for its optical-path difference. (a) Schematic view of the static modulated Fourier-transform spectrometer consisting of a modified Sagnac interferometer. S, source; SD, source driver; M1, fixed mirror; M2, displaced mirror; BS, beam splitter; FL, focusing lens; D, onedimensional detector; CI, computer interface; SI, sample interferogram; TM, transfer-function matrix of the spectrometer; RS, reconstructed spectrum. (b) Magnified optical layout near the one-dimensional detector array.
Keywords: Interferometer, Reconstruction, Spectrometry, Static modulation
OCIS codes: (000.4430) Numerical approximation and analysis; (070.4790) Spectrum analysis;(120.3180) Interferometry; (300.6300) Spectroscopy, Fourier transforms
Abstract
We introduce a spectral reconstruction method to enhance the spectral resolution in a static modulated Fourier-transform spectrometer. The optical-path difference and the interferogram in the focal plane, as well as the relationship of the interferogram and the spectrum, are discussed. Additionally, for better spectral reconstruction, applications of phase-error correction and apodization are considered. As a result, the transfer function of the spectrometer is calculated, and then the spectrum is reconstructed based on the relationship between the transfer function and the interferogram. The spectrometer comprises a modified Sagnac interferometer. The spectral reconstruction is conducted with a source with central wave number of 6,451 cm−1 and spectral width of 337 cm−1. In a conventional Fourier-transform method the best spectral resolution is 27 cm−1, but by means of the spectral reconstruction method the spectral resolution improved to 8.7 cm−1, without changing the interferometric structure. Compared to a conventional Fourier-transform method, the spectral width in the reconstructed spectrum is narrower by 20 cm−1, and closer to the reference spectrum. The proposed method allows high performance for static modulated Fourier-transform spectrometers.
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[하이라이트 논문] 한국광학회지 Vol. 33 No.3 (2022 June)
이중 링 Add/Drop 필터와 All-pass 지연 필터로 구성된 이차원 OCDMA 인코더/디코더
Two-dimensional OCDMA Encoder/Decoder Composed of Double Ring Add/Drop Filters and All-pass Delay Filters
정영철†
한국광학회지 Vol. 33 No.3 (2022 June) pp. 106-112
DOI: https://doi.org/10.3807/KJOP.2022.33.3.106
Fig. 1 Configuration of a 2-D optical code division multiple access (OCDMA) encoder/decoder composed of four cascaded double-ring add/ drop filters and three all-pass filters for delay operation.
Keywords: 집적 광학 소자, 광 코드분할 다중접속, 광 네트워크 보안, 전달 행렬 기법, 링 공진기
OCIS codes: (060.2330) Fiber optics communications; (060.4785) Optical security and encryption; (130.3120) Integrated optics devices; (130.7408) Wavelength filtering devices
초록
이중 링 add/drop 필터와 all-pass 지연 필터로 구성된 이차원 optical code division multiple access (OCDMA) 인코더/디코더를 제안하고, 설계 예시 및 수치해석을 통하여 실현 가능성을 확인하였다. 제안된 OCDMA 인코더/디코더의 칩 면적은 지연 도파로를 사용하는 기존 OCDMA 인코더/디코더에 비하여 1/3 정도로 줄어든다. 제안된 소자의 성능을 모델링하기 위하여 고속 푸리에 변환(fast Fourier transform, FFT) 및 전달 행렬 기법을 사용하였다. 정확한 코드로 디코딩된 펄스의 중심에서 자기상관 피크 값은 어긋난 파장 호핑 코드 및 스펙트럼 위상 코드로 디코딩된 경우의 최대 교차상관 레벨에 비하여 3배 이상으로 관측되었다. 이를 통하여 forward error correction (FEC) 한계에 해당하는 10−3이하의 비트 에러 오율을 얻을 수 있음을 알 수 있다.
Abstract
A two-dimensional optical code division multiple access (OCDMA) encoder/decoder, which is composed of add/drop filters and all-pass filters for delay operation, is proposed. An example design is presented, and its feasibility is illustrated through numerical simulations. The chip area of the proposed OCDMA encoder/decoder could be about one-third that of a previous OCDMA device employing delay waveguides. Its performance is numerically investigated using the transfer-matrix method combined with the fast Fourier transform. The autocorrelation peak level over the maximum cross-correlation level for incorrect wavelength hopping and spectral phase code combinations is greater than 3 at the center of the correctly decoded pulse, which assures a bit error rate lower than 10−3, corresponding to the forward error-correction limit.
