In a large-yield blast experiment, detonation velocity is an important index to estimate whether the large-scale explosives reach full detonation. An optical fiber test system for detonation velocity measurement is developed, which consists of optical fiber probes and a matched optical fiber detonation velocity meter. The system is used in a blast experiment of 81.5kg of TNT. All four fiber probes arranged achieve accurate signals. The experimental results indicate that the fiber system features anti-electromagnetic interference, high measuring precision, easy and safe operation, and low cost.
Phase noise characteristics for four-wave transmission in a long-haul interferometric fiber sensing system are
investigated. It is found that the phase noise in the presence and absence of four-wave mixing (FWM) is almost the same,
which indicates that the influence of FWM can be negligible. It is due to that the bandwidth of the photodetector used in
the fiber sensing system is often narrower than the beat frequency between FWM induced light and signal light, leading
the beat noise to be filtered. This noise characteristic is different from that in the fiber communication system and
provides guidance for the practical application of the interferometric fiber sensing system.
A Brillouin/erbium fiber laser (BEFL) of 25km single-mode fiber is constructed, and its characteristics of optical carrier
suppression are measured and analyzed. Light wave modulated by an electro-optic intensity modulator (EOIM) with
11GHz microwave frequency is adopted as the testing light. As much as 32 dB optical carrier-suppression ratio is
achieved at 112mW of 980nm pump power inside the BEFL. Meanwhile, the sideband powers remain nearly unchanged
in the process. Moreover, the carrier-suppression ratio is precisely controllable by tuning the 980nm pump power in the
BEFL. These optical carrier-suppression characteristics promise significant applications of such a technique not only to
distributed Brillouin optical fiber sensing based on EOIM but also to microwave photonic signal processing.
Two DFB semiconductor lasers are adopted as master and slave lasers to investigate the properties of the weak injection
locked DFB laser, such as the stable locking range, the phase noise and the power stability. A Brillouin/erbium fiber laser
pumped by the master DFB laser is injected into the slave DFB laser to validate the improvements of power stability and
spectral purity through the laser injection locking technology, which also demonstrates the feasibility of single frequency
extraction. The locked laser acts like a tunable narrow-band optical filter with central frequency and bandwidth decided
by the input signal. The experimental results give rise to some potential configurations useful for Brillouin distributed
fiber sensing and signal processing in microwave photonics.
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