Publication

Detrimental effect of self-phase modulation on the performance of Brillouin distributed fiber sensors

Luc Thévenaz, Stella Foaleng Mafang
2011
Journal Articles

Abstract

We show that the spectral broadening of the pump pulse through self-phase modulation in a time-domain distributed Brillouin sensor has a considerably detrimental effect in the measurement, especially in the case of long distances and high-resolution pulses. Using 30ns pump pulses with peak power of 276mW, self-phase modulation leads to a doubling of the effective gain linewidth after some 20km, which is equivalent to a contrast loss of 2dB in the measurement. The impact is higher for shorter pulses (higher resolution). The theoretical modeling is fully confirmed by experimental results.

Official source

https://infoscience.epfl.ch/entities/publication/10ecd234-fa0f-4517-893c-033f9f073b35

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Luc Thévenaz, Stella Foaleng Mafang
2011
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/10ecd234-fa0f-4517-893c-033f9f073b35

About this result

Related concepts (20)

Ultrashort pulse

In optics, an ultrashort pulse, also known as an ultrafast event, is an electromagnetic pulse whose time duration is of the order of a picosecond (10−12 second) or less. Such pulses have a broadband optical spectrum, and can be created by mode-locked oscillators. Amplification of ultrashort pulses almost always requires the technique of chirped pulse amplification, in order to avoid damage to the gain medium of the amplifier. They are characterized by a high peak intensity (or more correctly, irradiance) that usually leads to nonlinear interactions in various materials, including air.

Self-phase modulation

Self-phase modulation (SPM) is a nonlinear optical effect of light–matter interaction. An ultrashort pulse of light, when travelling in a medium, will induce a varying refractive index of the medium due to the optical Kerr effect. This variation in refractive index will produce a phase shift in the pulse, leading to a change of the pulse's frequency spectrum. Self-phase modulation is an important effect in optical systems that use short, intense pulses of light, such as lasers and optical fiber communications systems.

Mode locking

Mode locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds (10−12 s) or femtoseconds (10−15 s). A laser operated in this way is sometimes referred to as a femtosecond laser, for example, in modern refractive surgery. The basis of the technique is to induce a fixed phase relationship between the longitudinal modes of the laser's resonant cavity. Constructive interference between these modes can cause the laser light to be produced as a train of pulses.

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