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

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References

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  1. P. F. Kolesar and D. J. Mazzarese, �??Understanding Multimode Bandwidth and Differential Mode Delay Measurements and Their Applications,�?? in Proc. of the 51st International Wire and Cable Symposium of IWCS Inc., Lake Buena Vista, FL, 453�??460 (2002).
  2. C.-A. Bunge, J.-R. Kropp, and K. Petermann, �??Applicability of DMD-Measurements to New 10-Gigabit- Ethernet Fibres,�?? in Proc. 27th Eur. Conf. on Opt. Comm. (ECOC�??01), Amsterdam, The Netherlands, 362�?? 363 (2001).
  3. TIA-455-220-A, Differential Mode Delay Measurement of Multimode Fiber in the Time Domain, Telecommunication Industry Association (2003)
  4. S. D. Personick, �??Photon probe: An optical-fiber time-domain reflectometer,�?? Bell Syst. Tech. J. 56, 355�?? 366 (1977).
  5. D. Derickson, Fiber optic test and measurement, Hewlett-Packard professional books, Prentice Hall PTR, Upper Saddle River, New Jersey, 1998, USA, Chap. 11.
  6. R. Pass, N. Gisin, J. P. von der Weid, and H. H. Gilgen, �??Experimental and Theoretical Investigations of Coherent OFDR with Semiconductor Laser Sources,�?? J. Lightwave Technol. 12, 1622�??1630 (1994).
    [CrossRef]
  7. M. Yoshida, K. Nakamura, and H. Ito, �??A New Method for Measurement of Group Velocity Dispersion of Optical Fibers by Using a Frequency-Shifted Feedback Fiber Laser,�?? IEEE Photon. Technol. Lett. 13, 227�?? 229 (2001).
    [CrossRef]
  8. N. Zou, M. Yoshida, Y. Namibhira and H. Ito, �??PMD measurement based on delayed self-heterodyne OFDR and experimental comparison with ITU-T round robin measurements,�?? Electron. Lett. 38, 115�??116 (2002).
    [CrossRef]
  9. U. Glombitza and E. Brinkmeyer, �??Coherent Frequency-Domain Reflectometry for Characterization of Single-Mode Integrated-Optical Waveguides,�?? J. Lightwave Technol. 11, 1377�??1384 (1993).
    [CrossRef]
  10. L. Raddatz, I. H. White, D. G. Cunningham, and M. C. Nowell, �??An Experimental and Theoretical Study of the Offset Launch Technique for the Enhancement of the Bandwidth of Multimode Fiber Links,�?? J. Lightwave Technol. 16, 324�??331 (1998).
    [CrossRef]
  11. K. Shimizu, T. Horiguchi and Y. Koyamada, �??Measurement of Rayleigh Backscattering in Single-Mode Fibers Based on Coherent OFDR Employing a DFB Laser Diode.�?? IEEE Photon. Technol. Lett. 3, 1039�??1041 (1991).
    [CrossRef]

Bell Syst. Tech. J. (1)

S. D. Personick, �??Photon probe: An optical-fiber time-domain reflectometer,�?? Bell Syst. Tech. J. 56, 355�?? 366 (1977).

ECOC 2001 (1)

C.-A. Bunge, J.-R. Kropp, and K. Petermann, �??Applicability of DMD-Measurements to New 10-Gigabit- Ethernet Fibres,�?? in Proc. 27th Eur. Conf. on Opt. Comm. (ECOC�??01), Amsterdam, The Netherlands, 362�?? 363 (2001).

Electron. Lett. (1)

N. Zou, M. Yoshida, Y. Namibhira and H. Ito, �??PMD measurement based on delayed self-heterodyne OFDR and experimental comparison with ITU-T round robin measurements,�?? Electron. Lett. 38, 115�??116 (2002).
[CrossRef]

IEEE Photon. Technol. Lett. (2)

K. Shimizu, T. Horiguchi and Y. Koyamada, �??Measurement of Rayleigh Backscattering in Single-Mode Fibers Based on Coherent OFDR Employing a DFB Laser Diode.�?? IEEE Photon. Technol. Lett. 3, 1039�??1041 (1991).
[CrossRef]

M. Yoshida, K. Nakamura, and H. Ito, �??A New Method for Measurement of Group Velocity Dispersion of Optical Fibers by Using a Frequency-Shifted Feedback Fiber Laser,�?? IEEE Photon. Technol. Lett. 13, 227�?? 229 (2001).
[CrossRef]

J. Lightwave Technol. (3)

L. Raddatz, I. H. White, D. G. Cunningham, and M. C. Nowell, �??An Experimental and Theoretical Study of the Offset Launch Technique for the Enhancement of the Bandwidth of Multimode Fiber Links,�?? J. Lightwave Technol. 16, 324�??331 (1998).
[CrossRef]

U. Glombitza and E. Brinkmeyer, �??Coherent Frequency-Domain Reflectometry for Characterization of Single-Mode Integrated-Optical Waveguides,�?? J. Lightwave Technol. 11, 1377�??1384 (1993).
[CrossRef]

R. Pass, N. Gisin, J. P. von der Weid, and H. H. Gilgen, �??Experimental and Theoretical Investigations of Coherent OFDR with Semiconductor Laser Sources,�?? J. Lightwave Technol. 12, 1622�??1630 (1994).
[CrossRef]

Proc. of 51st IWCS 2002 (1)

P. F. Kolesar and D. J. Mazzarese, �??Understanding Multimode Bandwidth and Differential Mode Delay Measurements and Their Applications,�?? in Proc. of the 51st International Wire and Cable Symposium of IWCS Inc., Lake Buena Vista, FL, 453�??460 (2002).

Other (2)

TIA-455-220-A, Differential Mode Delay Measurement of Multimode Fiber in the Time Domain, Telecommunication Industry Association (2003)

D. Derickson, Fiber optic test and measurement, Hewlett-Packard professional books, Prentice Hall PTR, Upper Saddle River, New Jersey, 1998, USA, Chap. 11.

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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)

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

Equations (1)

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τ = f γ = f Δ υ T

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