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Using 255-bit Simplex-coded OTDR the authors demonstrate enhanced performance in Raman-based DTS ( 30 km with 5 K and 17 m resolution ) using low-power ( 80 mW ) laser-diodes.
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Improved Performance in Raman-based Distributed Temperature Sensing with coded OTDR and Discrete Raman Amplification
Gabriele Bolognini,Jonghan Park,Andrea Chiuchiarelli,Namkyoo Park,F. Di Pasquale +4 more
- 23 Oct 2006
TL;DR: Using 255-bit Simplex-coded OTDR, this article demonstrated enhanced performance in Raman-based DTS (30km with 5K and 17m resolution) using low-power (80 mW) laser-diodes.
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Abstract: Using 255-bit Simplex-coded OTDR we demonstrate enhanced performance in Raman-based DTS (30km with 5K and 17m resolution) using low-power (80 mW) laser-diodes. Additional discrete Raman amplification of coded pulses allows more than 40km measurement range.
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Figures
Fig. 3 reports the obtained OTDR traces for Anti-Stokes light with all sensing fiber spools kept at room temperature (300 K, black line), and with the two spools DSF-2 and DSF-4 heated at 340 K (gray line), showing the expected increase in Anti-Stokes intensity for the heated fiber spools. Fig. 3(a) reports the curves obtained with conventional OTDR and 180,000 time averages, Fig. 3(b) shows the traces obtained using 255 bit S-coded OTDR (80 mW peak power at sensing fiber input), and Fig. 3(c) the same traces in case of 255 bit S-coded OTDR and additional discrete Raman amplification of the OTDR signal (320 mW peak power at sensing fiber input). Note that for a sensible comparison of standard and coded OTDR techniques, a number of 706 time averaging has been used for a single codeword (255 orthogonal codewords are used), thus giving the same total number of 180,000 acquired traces as with conventional OTDR. 
Fig. 4 Temperature distribution versus fiber length obtained from measured traces using (a) conventional OTDR, (b) coded OTDR (255 bit Simplex codes), and (c) coded OTDR and lumped Raman amplification (DSF-2 and DSF-4 spools have been heated at 340 K). ![Figure 1 shows the experimental set-up used for implementing the Raman-based DTS system based on coded OTDR and lumped Raman amplification of OTDR coded pulses. An in-house-built PC-controlled OTDR board with a digital signal processor (DSP) was used to intensity-modulate the laser diode at 1550 nm according to the pulse patterns of Simplex coding [5], with 100 ns single bit pulse-width, as well as for implementing single pulses in conventional OTDR. The light source was a commercially available Fabry-Perot laser diode (FP-LD centered at 1550 nm, 80mW output power, 10 nm FWHM, thus preventing coherent speckles). The input pulses were injected into the sensing fiber through an optical circulator, and the backscattered lightwave signals were then coupled to the receiver after a largebandwidth band-pass filter (bandwidths are 1400-1510 nm for Anti-Stokes light and 1520-1600 nm for Rayleighscattered pump light). In this paper we compare the performance of standard OTDR, 255 bit S-coded OTDR and 255 bit S-coded OTDR combined with a discrete (or lumped) Raman amplification scheme (LRA), whose structure is schematically shown in Fig. 2, to provide low-noise optical amplification for the coded pulse pattern at 1550 nm, as explained below. The receiver, described in Fig. 1 (with improved performance with respect to [3]), is based on a high sensitivity InGaAs avalanche photodiode (APD), amplified by a high gain transimpedance amplifier (TIA), with about 3 MHz bandwidth. The estimated temperature sensitivity with this set-up was about 0.65%/K (at T=300 K). After the receiver block, an analog-to-digital converter (ADC) was used to sample the incoming analog data trace at 20 MHz. The code-imprinted traces were hence transmitted to the PC, where the de-coding process was carried out. The spatial resolution (defined by the measured 10%-90% response time) for the current DTS system was found to](/figures/figure-1-shows-the-experimental-set-up-used-for-implementing-1uhocjbl.png)
Figure 1 shows the experimental set-up used for implementing the Raman-based DTS system based on coded OTDR and lumped Raman amplification of OTDR coded pulses. An in-house-built PC-controlled OTDR board with a digital signal processor (DSP) was used to intensity-modulate the laser diode at 1550 nm according to the pulse patterns of Simplex coding [5], with 100 ns single bit pulse-width, as well as for implementing single pulses in conventional OTDR. The light source was a commercially available Fabry-Perot laser diode (FP-LD centered at 1550 nm, 80mW output power, 10 nm FWHM, thus preventing coherent speckles). The input pulses were injected into the sensing fiber through an optical circulator, and the backscattered lightwave signals were then coupled to the receiver after a largebandwidth band-pass filter (bandwidths are 1400-1510 nm for Anti-Stokes light and 1520-1600 nm for Rayleighscattered pump light). In this paper we compare the performance of standard OTDR, 255 bit S-coded OTDR and 255 bit S-coded OTDR combined with a discrete (or lumped) Raman amplification scheme (LRA), whose structure is schematically shown in Fig. 2, to provide low-noise optical amplification for the coded pulse pattern at 1550 nm, as explained below. The receiver, described in Fig. 1 (with improved performance with respect to [3]), is based on a high sensitivity InGaAs avalanche photodiode (APD), amplified by a high gain transimpedance amplifier (TIA), with about 3 MHz bandwidth. The estimated temperature sensitivity with this set-up was about 0.65%/K (at T=300 K). After the receiver block, an analog-to-digital converter (ADC) was used to sample the incoming analog data trace at 20 MHz. The code-imprinted traces were hence transmitted to the PC, where the de-coding process was carried out. The spatial resolution (defined by the measured 10%-90% response time) for the current DTS system was found to 
Fig. 5. RMS temperature resolution vs distance using conventional OTDR (squares), coded OTDR (circles), and coded OTDR with lumped Raman amplification (triangles).
![Figure 1 shows the experimental set-up used for implementing the Raman-based DTS system based on coded OTDR and lumped Raman amplification of OTDR coded pulses. An in-house-built PC-controlled OTDR board with a digital signal processor (DSP) was used to intensity-modulate the laser diode at 1550 nm according to the pulse patterns of Simplex coding [5], with 100 ns single bit pulse-width, as well as for implementing single pulses in conventional OTDR. The light source was a commercially available Fabry-Perot laser diode (FP-LD centered at 1550 nm, 80mW output power, 10 nm FWHM, thus preventing coherent speckles). The input pulses were injected into the sensing fiber through an optical circulator, and the backscattered lightwave signals were then coupled to the receiver after a largebandwidth band-pass filter (bandwidths are 1400-1510 nm for Anti-Stokes light and 1520-1600 nm for Rayleighscattered pump light). In this paper we compare the performance of standard OTDR, 255 bit S-coded OTDR and 255 bit S-coded OTDR combined with a discrete (or lumped) Raman amplification scheme (LRA), whose structure is schematically shown in Fig. 2, to provide low-noise optical amplification for the coded pulse pattern at 1550 nm, as explained below. The receiver, described in Fig. 1 (with improved performance with respect to [3]), is based on a high sensitivity InGaAs avalanche photodiode (APD), amplified by a high gain transimpedance amplifier (TIA), with about 3 MHz bandwidth. The estimated temperature sensitivity with this set-up was about 0.65%/K (at T=300 K). After the receiver block, an analog-to-digital converter (ADC) was used to sample the incoming analog data trace at 20 MHz. The code-imprinted traces were hence transmitted to the PC, where the de-coding process was carried out. The spatial resolution (defined by the measured 10%-90% response time) for the current DTS system was found to](/figures/figure-1-shows-the-experimental-set-up-used-for-implementing-1uhocjbl.webp)
Citations
Distributed temperature sensor system based on raman scattering using correlation-codes
Marcelo A. Soto,Prasant Kumar Sahu,Stefano Faralli,Gabriele Bolognini,F. Di Pasquale,B. Nebendahl,C. Rueck +6 more
TL;DR: A distributed sensor system employing spontaneous Raman scattering with use of correlation-coding techniques and a single-detector scheme is discussed and experimentally characterised.
Spatial resolution enhancement in fiber Raman distributed temperature sensor by employing ForWaRD deconvolution algorithm
TL;DR: In this article, the Fourier Wavelet Regularized Deconvolution (ForWaRD) method is employed to improve the spatial resolution in fiber Raman distributed temperature sensor without reducing the pulse width of the laser source.
45
High performance and highly reliable Raman based distributed temperature sensors based on correlation coded OTDR and multimode graded-index fibers
Marcelo A. Soto,Prasant Kumar Sahu,Stefano Faralli,G. Sacchi,Gabriele Bolognini,F. Di Pasquale,B. Nebendahl,C. Rueck +7 more
- 02 Jul 2007
TL;DR: In this paper, the performance of distributed temperature sensor systems based on spontaneous Raman scattering and coded OTDR is investigated, which uses graded-index multimode fibers, operates over short-to-medium distances (up to 8 km) with high spatial and temperature resolutions.
Lightning Location Method Using Orthogonal Coded Polarization Optical Time-Domain Reflectometer in Optical Fiber Transmission
Weihua Lian,Xingrui Su,Wei Li,Bin Wu,Xiaofang Feng,Hanqi Zhao,Desong Wang,Guilong Wu,Lin Liu,Yi-Tong Chen,Kaijing Hu +10 more
TL;DR: A polarization optical time-domain reflectometer (POTDR) method using orthogonal coding technology is proposed to improve lightning location accuracy in power transmission lines, achieving a location error of 200m in 20km sensing distance with enhanced distance and accuracy.
References
Using simplex codes to improve OTDR sensitivity
TL;DR: A coding technique for improving the sensitivity of optical time domain reflectometry (OTDR) using optical codes derived from Hadamard matrices and does not use correlation is proposed.
135
50-km single-ended spontaneous-Brillouin-based distributed-temperature sensor exploiting pulsed Raman amplification.
TL;DR: In this paper, a single-ended spontaneous-brillouin-intensity-based distributed temperature sensor with a sensing length of 50 km and a spatial resolution of 15 m was demonstrated by use of Raman amplification of the probe pulse within the sensing fiber.
51
A theoretical comparison of spontaneous Raman and Brillouin based fibre optic distributed temperature sensors
TL;DR: In this paper, it was shown that distributed temperature sensing based on Brillouin scattering offers considerably increased range beyond the theoretical limit of the spontaneous Raman based sensor, which is also temperature dependent and provides a signal which is an order of magnitude greater.
50
Analysis and experimental demonstration of simplex coding technique for SNR enhancement of OTDR
Duckey Lee,Hosung Yoon,Na Young Kim,Hansuek Lee,Namkyoo Park +4 more
- 27 Dec 2004
TL;DR: A practical algorithm was proposed and detailed equations were derived and an in-house OTDR board was developed to verify the proposed algorithm, and the experimental results showed excellent agreement with theory.
Transient effects in gain-clamped discrete Raman amplifier cascades
TL;DR: In this article, the dynamic characteristics of all-optically gain clamped discrete Raman amplifier chains are analyzed under channels add/drop conditions in large bandwidth WDM metro-core applications.