Expand this Topic clickable element to expand a topic
Skip to content
Optica Publishing Group

New optical frequency domain differential mode delay measurement method for a multimode optical fiber

Open Access Open Access

Abstract

A novel mode analysis method and differential mode delay (DMD) measurement technique for a multimode optical fiber based on optical frequency domain reflectometry has been proposed for the first time. We have used a conventional OFDR with a tunable external cavity laser and a Michelson interferometer. A few-mode optical multimode fiber was prepared to test our proposed measurement technique. We have also compared the OFDR measurement results with those obtained using a traditional time-domain measurement method.

©2005 Optical Society of America

Full Article  |  PDF Article
More Like This
Frequency-domain intermodal interferometer for the bandwidth measurement of a multimode fiber

Tae-Jung Ahn, Sucbei Moon, Soan Kim, Kyunghwan Oh, Dug Young Kim, Jens Kobelke, Kay Schuster, and Johnnes Kirchhof
Appl. Opt. 45(32) 8238-8243 (2006)

Optical frequency-domain chromatic dispersion measurement method for higher-order modes in an optical fiber

Tae-Jung Ahn, Yongmin Jung, Kyunghwan Oh, and Dug Young Kim
Opt. Express 13(25) 10040-10048 (2005)

Cited By

Optica participates in Crossref's Cited-By Linking service. Citing articles from Optica Publishing Group journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (5)

Fig. 1.
Fig. 1. A schematic diagram of an OFDR system for the measurement of the position of a fault in an SMF.
Fig. 2.
Fig. 2. Experimental set-up for DMD measurements of a multimode fiber.
Fig. 3.
Fig. 3. Refractive index profile of a few-mode fiber with a core diameter of ~8 µm and a maximum core index difference of ~0.026. The core diameter and the index difference were about 8 µm and 0.026, respectively. The core size of the FMF was designed to be same as that of the SMF to enable the coupling of the majority of reflected light from the FMF back into the SMF, whereas the refractive index of the FMF was designed to be higher than that of the SMF to support a few transverse modes. The length of the SMF in the reference arm was almost same as the length of FUT, which made the frequency of the beating signal very low. This decreased the phase noise in the measured beating signal [11]. The frequency component in the beating signal corresponds to the temporal delay associated with the difference in propagation time between modes. Solid line in Fig. 4 shows the modal delay of the FMF measured using our OFDR method. The intensity is normalized to the maximum peak intensity, and the time delay shown was divided by the sample length (40 m). There were four peaks observed, and the time delay of each mode is 16.5, 23.8, 26.9, and 30.8 ps/m, respectively. This indicates that there exist four transverse modes in the FMF corresponding to these four different modal propagation speeds. This modal delay measurement can be used to calculate the propagation constant for each transverse mode of the fiber. Dashed line in Fig. 4 shows the modal delay of the same FMF measured using a conventional time-domain method. A gain-switched laser (OPG-1500, Optune Inc.) was used as the input pulse source operating at λ=1550 nm, with an FWHM=28 ps and a 10 MHz repetition rate. It shows that the input pulse was split into three pulses in the time-domain, with time delays of 16.4, 27.9 and 32.0 ps/m, respectively.
Fig. 4.
Fig. 4. Modal delay measurements of an FMF in frequency domain using an OFDR, and time domain using an optical pulse source without bending a sample fiber.
Fig. 5.
Fig. 5. Modal delay measurements of an FMF in frequency domain using an OFDR, and time domain using an optical pulse source with bending of a sample fiber.

Tables (1)

Tables Icon

Table 1. A comparison of the results of the frequency-domain method with the results of the time-domain method.

Equations (1)

Equations on this page are rendered with MathJax. Learn more.

τ = f γ = f Δ υ T
Select as filters


Select Topics Cancel
© Copyright 2024 | Optica Publishing Group. All Rights Reserved