Research Progress of φ-OTDR Noise Reduction Processing

Ke Li; Yandong Gong; Zhuo Zhang

doi:10.3788/LOP202259.2300002

Journals >Laser & Optoelectronics Progress >Volume 59 >Issue 23 >Page 2300002 > Article

Laser & Optoelectronics Progress
Vol. 59, Issue 23, 2300002 (2022)

Research Progress of φ-OTDR Noise Reduction Processing

Ke Li, Yandong Gong^*, and Zhuo Zhang

Author Affiliations

School of Instrument Science and Opto-Electronic Engineering, Beijing Information Science and Technology University, Beijing 100192, China

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DOI: 10.3788/LOP202259.2300002 Cite this Article Set citation alerts

Ke Li, Yandong Gong, Zhuo Zhang. Research Progress of φ-OTDR Noise Reduction Processing[J]. Laser & Optoelectronics Progress, 2022, 59(23): 2300002 Copy Citation Text

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Fig. 1. Sensing system of the φ-OTDR

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Fig. 2. Generation mechanism of the coherent noise^[11]

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Fig. 3. Generation mechanism of the polarization noise^[12-14]

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Fig. 4. Experimental system based on coherent detection^[15]

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Fig. 5. Schematic diagram of the TGD-OFDMR system^[18]

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Fig. 6. Experimental setup for bipolar coding ^[20]

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Fig. 7. φ-OTDR sensing system based on few-mode fiber space division multiplexing^[30]

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Fig. 8. φ-OTDR system based on orthogonal polarization switching^[32]

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Classification	Cause of noise	Whether it is the main component of system noise
Coherent noise	RBS caused by phase length or cancellation of pulse light detected at different positions of optical fiber	yes
Polarization noise	when the polarization state of the pulse light is orthogonal, the interference light intensity disappears completely	yes
Common mode noise	caused by frequency drift of laser source or environmental change along the optical fiber	no
Light source noise	caused by unsatisfactory bandwidth of light source or insufficient extinction ratio	no

Table 1. Classification and definition of various main noises

Ref.	Suppress result	Advantage	Disadvantage	Room of improvement
［15］	compared with the amplitude extraction method, SNR is increased by 11 dB	it is easy to obtain the spatial information of vibration points by using the virtual peak discrimination method	only the false alarm is eliminated, and high fidelity signal reconstruction is not fundamentally realized	strengthen the screening of discriminant points to achieve correct virtual peak reconstruction
［19］	SNR is up to 26 dB, and the spatial resolution is close to 5 m	system has low complexity and low cost	the accuracy of time control gate circuit is not ideal	can be combined with high-speed camera
［20］	SNR increased by 7.1 dB, measurement time halved	frequency drift compensation by spectrum extraction	spatial resolution of the system is not ideal	introduction of less mode fiber for light wave transmission
［30］	phase error caused by interference fading is completely eliminated	system structure is simple by combining space division multiplexing and few mode fiber	transmission distance is low, and the uneven scattering points of the optical fiber are not considered	consider combining multimode fiber with frequency division multiplexing technology

Table 2. Typical coherent fading suppression techniques

Ref.	Suppress result	Advantage	Disadvantage	Room of improvement
［32］	SNR increased by 15 dB	polarization dependence of signal intensity using Rayleigh interference	structure of the experimental system is complex，and the demodulation signal processing formula is complex	introducing polarization multiplexing technology based on orthogonal polarization switching
［34］	polarization fading can be effectively eliminated in sensitive areas	combining PMF with SOP for noise reduction	interference caused by SOP small circle rotation is not completely eliminated	reduce the angle and number of SOP rotations
［35］	insensitive to polarization effect	sensor with dual polarization multiplexing	polarization diversity sensing structure is not considered	introducing time division multiplexing technology into the structure with polarization diversity

Table 3. Typical polarization fading suppression techniques

Ref.	Suppress result	Advantage	Disadvantage	Room of improvement
［38］	avoid the effect of too many pulses on common mode noise	applying the DCM to common mode rejection	poor spatial resolution and can not be applied to long-distance sensing	can combine radiosonde technology with frequency division multiplexing
［39］	strong signal acquisition capability and low noise	signal transmission using Mini-DAS module	influence of seabed pressure on the pressure along the optical fiber is not considered	for seabed inspection, the entire optical fiber shall be coated with compressive materials

Table 4. Typical common mode noise suppression techniques

Type	Whether it is the main component of noise？	Advantage	Disadvantage	Future direction
Coherent noise	yes	space division multiplexing technology based on few mode fiber	coherence of various high-order modes or same order modes of space division multiplexing is too high	combination of multi-core fiber and time division multiplexing technology
Polarization noise	yes	technology of transforming single mode fiber into polarization maintaining fiber	disturbance caused by different polarization states cannot be eliminated	transformation of polarization maintaining fiber using polarization multiplexing technology
Common mode noise	no	Mini-DAS module technology	limited light wave signal transmission	introducing frequency division multiplexing technology
Light source noise	no	time delay interferometry	amplified light source signal frequency is difficult to meet the requirements	combining high-speed camera with ultra-low frequency drift light source