VAD technology for laser fibers are offering the extremely large rare-earth doped core, which makes it possible to improve the productivity and reproducibility of laser fibers. At the previous report, Yb:Ce co-doped fibers have shown relatively large background loss and the issues of surface crystallization. In this report, the additional process development for the reduction of the loss and the efficiency improvement has been successful. Based in that, Yb:Ce codoped aluminosilicate PM fiber has been fabricated and it used for power amplification of narrow linewidth source. The slope efficiency was 72.8% w.r.t the absorbed pump power and the output power has been reached to 124W at the initial experiment. The further power scaling will be performed and SBS characterization will be reviewed.
VAD technology has been proposed for laser fiber fabrication to improve its productivity and reproducibility. Rare-earth ion, Yb3+ has been incorporated with Ce3+ and Al3+ by the conventional solution doping process. In order to obtain a transparent Yb-doped core rod, the pre-sintering and consolidation process for the large volume of silica soot deposited by VAD has been significantly investigated. In addition, 20/400μm Yb-doped fiber with octagonal cladding has been fabricated. The cladding absorption was 0.44dB/m at 915nm, which corresponds to ~ 0.2mol% of Yb concentration and the slope efficiency with respect to absorbed pump power at 976nm was 66.7%.
We have proposed the systematic measurement of coating geometry for specialty fibers based on dark field illumination technique. The measured dark-field projection image shows clear interfaces between different refractive index materials. Using own developed image processing tool, the interfaces automatically detected and analyzed. Every degree of measurements provides circularity of each layer and then shows the center point of individual layer. Using this technique, coating diameter, coating non-circularity and coating ellipticity for double clad fiber were successfully measured and high resolution camera also detected some of existing coating defect and delamination.
A discretely tunable fiber ring laser based on a Sagnac interferometer incorporating a few-mode polarization maintaining
fiber and semiconductor optical amplifier as the gain media is presented. Nine lasing wavelengths at a tuning step of 2.5
nm is achieved with side-mode suppression ratio over 20 dB.
We propose a novel approach for resolving temperature and strain variations by use of Sagnac interferometer incorporating
two types of high birefringence fibers (HBFs) and a polarization controller. The two types of HBFs are spliced
together to act as the sensing head for temperature and strain discrimination. The detected parameters are two wavelength
dips over a broad wavelength range in the transmission spectrum of the Sagnac interferometer, whose sensitivity
responses to temperature and strain both depend on those of the two HBFs. As a result, the sensitivity responses can be
controlled by adjusting the polarization controller adjacent to the sensing head to shift the wavelength dips and then
change their degrees of dependence on the two HBFs.
We report an intensity based fiber strain sensor using a long period grating (LPG) pair along with an in-line core mode
blocker. By sandwiching the core mode blocker fabricated by arc method between a LPG pair, an band-pass filter was
formed. Measured by optical power meter at one specific wavelength, the transmitted power was found to decrease as a
variation of axial strain is applied on one single LPFG, therefore we can measure the applied strain by measuring the
transmitted power. The measured response of voltage for change of strain was 6.37pV/ με.
We report a fiber sensor capable of simultaneously measuring temperature and strain. A fiber Bragg grating (FBG) was
incorporated in a Lyot fiber filter (LFF) by fusion splicing a section of high birefringence fiber (PM fiber) with an FBG
and then placing them between 2 polarizers. Measured in the transmission mode, the fringe resulted from the LFF and
the resonance wavelength dip of the FBG has different responses when a variation of temperature or strain is applied.
The proposed device can therefore measure both strain and temperature simultaneously.
A feedback high birefringence fiber loop mirror is proposed and theoretically analyzed. Large effective free spectral
range can be achieved by the intrinsic vernier effect between the fast and slow axes in the high birefringence fiber,
which is independent of the input signal polarization.
We investigate the effects of co-doping of boron on the index difference between the core and cladding of the optical fiber, the temperature and bending sensitivities of a long-period fiber grating (LPFG), and the resonance wavelength separation between the core mode and the first cladding mode of a fiber Bragg grating (FBG). We observe that the index difference between the core and cladding decreases with the slope of 1.69×10−4/SCCM and that the temperature sensitivity of the resonance wavelength shift of LPFG decreased with the slope of 0.01145 nm/°C/SCCM. The measurement results indicate that, as the amount of the co-doped boron is increased, the bending sensitivity of LPFGs increases, while the resonance wavelength separation between the core mode and the first cladding mode of FBGs decreases. These results may be used for design of Ge-B co-doped optical fibers with the desired characteristics suitable for optical fiber communication and sensing applications.
We propose a simple semiconductor optical amplifier–based fiber laser configuration for achieving multiwavelength oscillation at room temperature, in which a few-mode fiber Bragg grating was used as the wavelength-selective component. An amplitude variation of 0.8 dB over a 180-sec period was obtained for triple-wavelength oscillation at room temperature, which is more stable than that of erbium doped fiber (EDF)–based fiber laser with similar configuration. This multiwavelength laser can be switched between dual- and triple-wavelength operations by properly adjusting the polarization controller in the cavity. The lasing wavelength could be effectively tuned using the thermal heating method, and the output power variation was very small compared with that of the EDF-based fiber laser. This multiwavelength laser has the advantage of simple configuration, good stability, and wavelength tuning with small output power variation.
The novel multi-wavelength SOA-fiber laser based on a linear- or ring-cavity incorporating a few-mode fiber Bragg grating or a sampled chirped fiber Bragg grating, respectively, is demonstrated. The proposed SOA-fiber laser offers advantages such as simple structure, low loss, multi-wavelength lasing lines with moderate output power.
We will discuss in this presentation a novel and simple erbium-doped fiber laser configuration for multi-wavelength oscillation at room temperature, in which a few-mode fiber Bragg grating was used as the wavelength-selective component. This multi-wavelength laser can be switched between dual- and triple-wavelength operations by properly adjusting polarization controller in the cavity. By using stain- or temperature-induced few-mode fiber grating, we also demonstrate a tunable multi-wavelength laser based on the proposed scheme. This multi-wavelength laser has the advantage of simple configuration, high stability, low cost and stable operation at room temperature.
We present an upstream transmission method independent of temperature characteristics of the remote node (RN) in a WDM-PON. This method employs a self-injection locked Fabry-Perot laser diode (F-P LD) for upstream transmission in the optical network unit (ONU). Using this method, the sidemodes of the F-P LD are suppressed, and the F-P LD is matched to the center wavelength of the wavelength distributor/combiner placed at the RN. The experimental results confirm that bidirectional error-free transmission at 1.25/10 Gbit/s could be achieved.
It is reported that the spectral loss of a photonic crystal fiber having a large hole-to-hole distance (~10 micron) is sensitive to micro- and macrobending on the fiber. For the macrobending experiment, the fiber was simply wound round a circular structure of known radius, which was reduced up to a few centimeters. As the bending radius was decreased, the transmission loss was increased. In terms of wavelength, the spectral loss was rather flat, which looked suitable for a wide-band fiber attenuator. For the microbending case, a series of regularly spaced silica rods was attached on a slide glass and pressed against the fiber by loading a series of metal plates of known mass on the glass. With this scheme, it was possible to induce periodic microbending on the photonic crystal fiber. The silica rods had the same diameter of a few hundred microns and spaced by about 500 micron. The bending loss was increased by adding the weight. The photonic crystal fiber having a large hole-to-hole distance was found to be highly sensitive to both microbending and macrobending when compared to the conventional single-mode fiber. In this paper, we will discuss the microbending effect on the photonic crystal fiber with various experimental conditions, such as the periodicity and the length of the microbend-inducing region.
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