A semiconductor QD fiber amplifier (SQDFA) is proposed and theoretically researched. The fiber amplifier makes use
of a tapered twin SMF coupler and a PbS QD-film is coated on the surface of it. In the tapered region, QDs will be
excited by the evanescent wave of a pump and produce a gain on signal. The fiber coupler is properly designed to ensure
a desired power ratio of the output signal. Using a 1530-nm signal and a 980-nm pump, an optical gain of about 8 dB is
achieved with a gain efficiency of 3.48dB/cm. This SQDFA has unique advantages including suppression to the
amplified spontaneous emission (ASE), simple fabrication and lower insertion loss and thus has a great potential in fiber
communication systems.
Based on semiconductor quantum dots and a tapered optical fiber, an optical fiber amplifier was proposed and studied in
this paper. It was fabricated by coating PbS quantum dots doped sol-gel onto the tapered region of optical fiber. The PbS
quantum dots were synthesized by colloidal method. The tapered optical fiber was made by using a standard single mode
fiber through heating of CO2 laser. With a Wavelength Division Multiplexer (WDM), a signal and a pump can be
injected into the fiber tapered region and interacts with the quantum dots through the evanescent field so that the signal
can be amplified. The optical gain was characterized and more than 10dB gain was obtained at 1310nm with only 1.6cm
interacting length at 130mw pump power.
A strain sensor based on cladding mode resonance of optical double-cladding fiber (DCF) was proposed and
experimentally demonstrated. The sensor head was fabricated by splicing a section of DCF into a standard single mode
fiber (SMF). Attributed to the thin thickness of the inner cladding, the core mode can be coupled with cladding modes
which generatess a strong resonant spectrum at the phase-matching wavelength. When the DCF sensor is applied an axial
strain, the refractive index of the DCF decreases due to the photoelastic effect. According to the coupled mode theory, the
phase-matching wavelength will shift to a shorter wavelength. By detecting the resonant spectrum variation, the stain
sensor can be realized. The strain sensitivity was achieved as -2.87 pm με over 800με measurement range with good
repeatability. With the simple configuration and attractive performance, the specialty DCF strain sensor can be explored
for wide sensing applications.
In this paper, a new method was proposed to fabricate tapered optical fiber which has strong evanescent field in the
tapered region. Our system relies on a scanned high-frequency pulsed carbon dioxide laser (CO2 laser) beam across the
taper region. The optimal heating and stretching parameters were determined through a series experiments. An effective
laser scanning pattern was designed to obtain a relatively uniform temperature field. Symmetrical fiber tapers with taper
waist diameters of ~10-20μm, overall lengths of ~10-17mm and transmission losses of ~0.8-3dB at 1550nm were
obtained. The taper profile was measured which presents a good fit with the "decaying-exponential" model. The "selfregulating"
law is demonstrated, which shows the desired taper waist diameter as a function of the laser power. A refractive index sensing experiment using the tapered optical fiber is also studied to show the potential application in refractive index sensor.
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