## Centimeter-level spatial resolution over 40 km realized by bandwidth-division phase-noise-compensated OFDR |

Optics Express, Vol. 19, Issue 20, pp. 19122-19128 (2011)

http://dx.doi.org/10.1364/OE.19.019122

Acrobat PDF (1441 KB)

### Abstract

We present a bandwidth-division phase-noise-compensated optical frequency domain reflectometry (PNC-OFDR) technique, which permits a fast sweep of the optical source frequency. This method makes it possible to reduce the influence of environmental perturbation, which is the dominant factor degrading the spatial resolution of frequency-domain reflectometry at a long measurement range after compensation of the optical source phase noise. By using this approach, we realize a sub-cm spatial resolution over 40 km in a normal laboratory environment, and a 5 cm spatial resolution at 39.2 km in a field trial.

© 2011 OSA

## 1. Introduction

1. M. K. Barnoski and S. M. Jensen, “Fiber waveguides: a novel technique for investigating attenuation characteristics,” Appl. Opt. **15**(9), 2112–2115 (1976). [CrossRef] [PubMed]

2. B. Huttner, J. Reecht, N. Gisin, R. Passy, and J. P. von der Weid, “Local birefringence measurements in single-mode fibers with coherent optical frequency-domain reflectometry,” IEEE Photon. Technol. Lett. **10**(10), 1458–1460 (1998). [CrossRef]

3. W. Eickhoff and R. Ulrich, “Optical frequency domain reflectometry in single‐mode fiber,” Appl. Phys. Lett. **39**(9), 693–695 (1981). [CrossRef]

5. G. Mussi, N. Gisin, R. Passy, and J. P. von der Weid, “-152.5 dB sensitivity high dynamic-range optical frequency-domain reflectometry,” Electron. Lett. **32**(10), 926–927 (1996). [CrossRef]

7. K. Tsuji, K. Shimizu, T. Horiguchi, and Y. Koyamada, “Spatial-resolution improvement in long range coherent optical frequency domain reflectometry by frequency-sweep linearisation,” Electron. Lett. **33**(5), 408–409 (1997). [CrossRef]

8. X. Fan, Y. Koshikiya, and F. Ito, “Phase-noise-compensated optical frequency domain reflectometry with measurement range beyond laser coherence length realized using concatenative reference method,” Opt. Lett. **32**(22), 3227–3229 (2007). [CrossRef] [PubMed]

9. X. Fan, Y. Koshikiya, and F. Ito, “Noise of long-range optical frequency domain reflectometry after optical source phase noise compensation,” Proc. SPIE **7503**, 75032E, 75032E-4 (2009). [CrossRef]

## 2. Principle

8. X. Fan, Y. Koshikiya, and F. Ito, “Phase-noise-compensated optical frequency domain reflectometry with measurement range beyond laser coherence length realized using concatenative reference method,” Opt. Lett. **32**(22), 3227–3229 (2007). [CrossRef] [PubMed]

*X*(

_{N}*t*), which are calculated using the following expression:

*X*(

_{1}*t*) is a phase term obtained from an auxiliary interferometer with a delay time

*τ*in one arm. The phase noise term Φ(

_{ref}*t*) is compensated from

*θ*(

*t*) –

*θ*(

*t*-

*τ*) to the following term:

_{FUT}*τ*is the time needed for a round-trip in the FUT. When

_{FUT}*τ*is equal to

_{FUT}*Nτ*, the phase noise term is canceled out and the optimum compensation can be achieved.

_{ref}*m*-th (

*m*= 2, 3,…, M) section so that it is within a frequency of 0 < f

_{base }< F/M, we only need a sampling card with a sampling rate of 2F/M. Meanwhile, the amount of data decreases to 1/M compared with that required when using the conventional sampling method.

*X*(

_{N}*t*) is no longer the correct reference to compensate for the phase noise in the down-converted signal. To obtain the correct reference, we should also down-convert the frequency of

*X*(

_{N}*t*) by the same value. This can be realized by changing

*X*(

_{N}*t*) as follows:

*X*(

_{N}*t*) for compensation. Although the two methods are equivalent to each other and can be implemented digitally, we adopt the former because it consumes fewer calculation resources.

## 3. Experimental setup

^{TM}) and the linewidth measured using the self-delay heterodyne method with a 100 km delay fiber is 4 kHz. If we assume that the lineshape is Lorentzian, the measurement range of regular OFDR can be estimated to be c/2nπΔf as 8.0 km while considering the round-trip path, where c is the speed of light in vacuum, n is the refractive index of FUT, Δf is the linewidth. A single sideband with a suppressed carrier (SSB-SC) modulator and a frequency swept RF synthesizer are used for external frequency sweeping. The sweep rate is set at 3 THz/s, which is 7.5 times faster than that used previously [10], with a full sweep frequency of 15 GHz (limited by available bandwidth of the modulator) for a 5-ms acquisition time. The ratio of beat frequency to distance is determined by the sweep rate to be 2nγ/c as 300 Hz/cm, where γ is the sweep rate. If we consider the calculation process, after applying Eq. (1) and the round-off for later averaging, the useful part is 12.5 GHz (4.17 ms acquisition time), corresponding to a theoretical spatial resolution of 8 mm (240 Hz in frequency domain). A Mach-Zehnder interferometer with a 5-km delay fiber in one arm is used as an auxiliary interferometer for compensation, and is placed in a soundproof box to insulate it from acoustic noise. The main interferometer consists of a local arm and a measurement arm, which is equipped with a circulator for launching the light wave into the FUT and receiving the reflected signal. A polarization controller is used in the local arm to control the power of the local light so that it is split evenly by the polarization splitters, which are important elements of a polarization diversity scheme, adopted to remove the influence of the polarization effect. The signals from both the auxiliary and main interferometers are detected by balanced photodetectors (BPDs). Then, the signals from the auxiliary interferometer are filtered by a low-pass filter (LPF), sampled by using an analog-to-digital card (ADC), and collected by a computer. On the contrary, the signals from the main interferometers must undergo bandwidth-division processing before being sampled by the ADCs. The details of the process are given in the next paragraph.

## 4. Experimental results

*N*× 2.5 km), which is an optimum compensation position, a 3-dB spatial resolution of 8 mm (240 Hz in frequency domain) is obtained in a normal environment and it deteriorates to about 2.5 cm (750 Hz in frequency domain) in a relatively noisy environment. For the reflection peaks that occur around 41.25 km ((

*N*+ 0.5) × 2.5 km), which is the border of the 16th compensation section, the spatial resolution is still 8 mm in a normal environment, and it deteriorates to about 5 cm (1500 Hz in frequency domain) in a relatively noisy environment.

## 5. Summary

## References and links

1. | M. K. Barnoski and S. M. Jensen, “Fiber waveguides: a novel technique for investigating attenuation characteristics,” Appl. Opt. |

2. | B. Huttner, J. Reecht, N. Gisin, R. Passy, and J. P. von der Weid, “Local birefringence measurements in single-mode fibers with coherent optical frequency-domain reflectometry,” IEEE Photon. Technol. Lett. |

3. | W. Eickhoff and R. Ulrich, “Optical frequency domain reflectometry in single‐mode fiber,” Appl. Phys. Lett. |

4. | H. Barfuss and E. Brinkmeyer, “Modified optical frequency domain reflectometry with high spatial resolution for components of integrated optic systems,” J. Lightwave Technol. |

5. | G. Mussi, N. Gisin, R. Passy, and J. P. von der Weid, “-152.5 dB sensitivity high dynamic-range optical frequency-domain reflectometry,” Electron. Lett. |

6. | D. K. Gifford, M. E. Froggatt, M. S. Wolfe, S. T. Kreger, and B. J. Soller, “Millimeter resolution reflectometry over two kilometers,” in |

7. | K. Tsuji, K. Shimizu, T. Horiguchi, and Y. Koyamada, “Spatial-resolution improvement in long range coherent optical frequency domain reflectometry by frequency-sweep linearisation,” Electron. Lett. |

8. | X. Fan, Y. Koshikiya, and F. Ito, “Phase-noise-compensated optical frequency domain reflectometry with measurement range beyond laser coherence length realized using concatenative reference method,” Opt. Lett. |

9. | X. Fan, Y. Koshikiya, and F. Ito, “Noise of long-range optical frequency domain reflectometry after optical source phase noise compensation,” Proc. SPIE |

10. | Y. Koshikiya, X. Fan, and F. Ito, “Influence of acoustic perturbation of fibers in phase-noise-compensated optical-frequency-domain reflectometry,” J. Lightwave Technol. |

**OCIS Codes**

(060.2300) Fiber optics and optical communications : Fiber measurements

(120.1840) Instrumentation, measurement, and metrology : Densitometers, reflectometers

**ToC Category:**

Fiber Optics and Optical Communications

**History**

Original Manuscript: June 8, 2011

Revised Manuscript: August 23, 2011

Manuscript Accepted: August 23, 2011

Published: September 16, 2011

**Citation**

Xinyu Fan, Yusuke Koshikiya, and Fumihiko Ito, "Centimeter-level spatial resolution over 40 km realized by bandwidth-division phase-noise-compensated OFDR," Opt. Express **19**, 19122-19128 (2011)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-20-19122

Sort: Year | Journal | Reset

### References

- M. K. Barnoski and S. M. Jensen, “Fiber waveguides: a novel technique for investigating attenuation characteristics,” Appl. Opt.15(9), 2112–2115 (1976). [CrossRef] [PubMed]
- B. Huttner, J. Reecht, N. Gisin, R. Passy, and J. P. von der Weid, “Local birefringence measurements in single-mode fibers with coherent optical frequency-domain reflectometry,” IEEE Photon. Technol. Lett.10(10), 1458–1460 (1998). [CrossRef]
- W. Eickhoff and R. Ulrich, “Optical frequency domain reflectometry in single‐mode fiber,” Appl. Phys. Lett.39(9), 693–695 (1981). [CrossRef]
- H. Barfuss and E. Brinkmeyer, “Modified optical frequency domain reflectometry with high spatial resolution for components of integrated optic systems,” J. Lightwave Technol.7(1), 3–10 (1989). [CrossRef]
- G. Mussi, N. Gisin, R. Passy, and J. P. von der Weid, “-152.5 dB sensitivity high dynamic-range optical frequency-domain reflectometry,” Electron. Lett.32(10), 926–927 (1996). [CrossRef]
- D. K. Gifford, M. E. Froggatt, M. S. Wolfe, S. T. Kreger, and B. J. Soller, “Millimeter resolution reflectometry over two kilometers,” in 33rd European Conference and Exhibition on Optical Communication—ECOC 2007 (2007), vol. 2, pp. 85–87, paper Tu.3.6.1.
- K. Tsuji, K. Shimizu, T. Horiguchi, and Y. Koyamada, “Spatial-resolution improvement in long range coherent optical frequency domain reflectometry by frequency-sweep linearisation,” Electron. Lett.33(5), 408–409 (1997). [CrossRef]
- X. Fan, Y. Koshikiya, and F. Ito, “Phase-noise-compensated optical frequency domain reflectometry with measurement range beyond laser coherence length realized using concatenative reference method,” Opt. Lett.32(22), 3227–3229 (2007). [CrossRef] [PubMed]
- X. Fan, Y. Koshikiya, and F. Ito, “Noise of long-range optical frequency domain reflectometry after optical source phase noise compensation,” Proc. SPIE7503, 75032E, 75032E-4 (2009). [CrossRef]
- Y. Koshikiya, X. Fan, and F. Ito, “Influence of acoustic perturbation of fibers in phase-noise-compensated optical-frequency-domain reflectometry,” J. Lightwave Technol.28, 3323–3328 (2010).

## Cited By |
Alert me when this paper is cited |

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

« Previous Article | Next Article »

OSA is a member of CrossRef.