title: Low coherent hybrid detection technique for differential mode delay in a multimode optical fiber.
abstract: We present a low coherent hybrid detection technique for the differential model delay (DMD) measurement of a conventional optical multimode fiber with a modified Mach-Zehnder interferometer. A low coherent hybrid detection technique enhances mode coupling between guided modes and the reference mode to easily resolve the modal distribution. An optical spectrum analyzer and a broadband source were used to obtain time-resolved optical beat signals. The measured interference signal was Fourier transformed to obtain time-delay information. A scanning offset launching method was used to excite every available mode in a multimode fiber (MMF). Measurements of a conventional 8-m-long MMF demonstrated the validity of our proposed method. The experimental results of our proposed method agree well with results obtained using a conventional time domain measurement method. Our proposed method can be used to measure the DMD in a short length of optical MMF with a temporal resolution better than 0.72 ps when using an 8-m-long single-mode fiber as a reference.
authors.affiliation: Department of Information and Communications, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712, South Korea. jylee@gist.ac.kr
authors.forename: J Y
authors.initials: JY
authors.lastname: Lee
authors.forename: T-J
authors.initials: TJ
authors.lastname: Ahn
authors.forename: D Y
authors.initials: DY
authors.lastname: Kim
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis / Q000295:instrumentation* / Q000379:methods*; D005336:Fiber Optic Technology / Q000295:instrumentation*; D055100:Optical Fibers; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors; D041623:Tomography, Optical Coherence / Q000295:instrumentation* / Q000379:methods