A distributed optical fibre sensor is introduced which is capable of quantifying multiple dynamic strain perturbations along 1 km of a sensing fibre simultaneously using a standard telecommunication single-mode optical fibre. The technique is based on measuring the phase between the Rayleigh scattered light from two sections of the fibre which define the gauge length. The phase is spatially determined along the entire length of the fibre with a single pulse. This allows multiple moving strain perturbation to be tracked and quantified along the entire length of the fibre. The demonstrated setup has a spatial resolution of 2 m with a frequency range of 500-5000 Hz. The minimum detectable strain perturbation of the sensor was measured to be 80 n .

Sp1-like transcription factors are characterized by three highly homologous C-terminal zinc finger motifs that bind GC-rich sequences. These proteins behave as either activators or repressors and have begun to be classified into different subfamilies based upon the presence of conserved motifs outside the zinc finger domain. This classification predicts that different Sp1-like subfamilies share certain functional properties. TIEG1 and TIEG2 constitute a new subfamily of transforming growth factor-␤-inducible Sp1-like proteins whose zinc finger motifs also bind GC-rich sequences. However, regions outside of the DNA-binding domain that differ in structure from other Sp1-like family members remain poorly characterized. Here, we have used extensive mutagenesis and GAL4-based transcriptional assays to identify three repression domains within TIEG1 and TIEG2 that we call R1, R2, and R3. R1 is 10 amino acids, R2 is 12 amino acids, and R3 is approximately 80 amino acids long. None of these domains share homology with previously described transcriptional regulatory motifs, but they share strong sequence homology and are functionally conserved between TIEG1 and TIEG2. Together, these data demonstrate that TIEG proteins are capable of repressing transcription, define domains critical for this function, and further support the idea that different subfamilies of Sp1-like proteins have evolved to mediate distinct transcriptional functions.Sp1-like transcription factors have recently elicited significant attention because of their widespread participation in the regulation of mammalian cell homeostasis (1). Members of this family of proteins currently include Sp1-4, BTEB1, BTEB2/ IKLF, TIEG1/MGIF, TIEG2, BKLF, EKLF, GKLF/EZF, LKLF, CPBP/Bcd, and AP2-rep, all of which are characterized by three highly conserved C 2 H 2 zinc finger DNA-binding domains at their C termini (2-21). Sp1-like transcription factors share over 75% similarity within these three zinc finger domains. Because of this high similarity, it is not surprising that many of these proteins bind to similar GC-rich sequences within promoters (reviewed in Ref. 1). These GC-rich sequences contribute to the regulation of a large number of genes necessary for various cellular functions, including cell proliferation, differentiation, and apoptosis (22). Thus, because of their participation in these functions, many Sp1-like proteins also function as key regulators of morphogenesis (1).While the DNA-binding domain of the Sp1-like transcription factor family is highly conserved, the N-terminal regions of the proteins are more divergent. Interestingly, it is through this domain that many of these transcription factors regulate transcription (7,14,(17)(18)(19)(23)(24)(25)(26)(27)(28)(29)(30). The founding member of this family, Sp1, for example, is a potent transcriptional activator that utilizes glutamine-rich sequences located within its N terminus to interact with proteins from the basal transcriptional apparatus to regulate gene expression (23). In contrast, BKLF behaves a...

We demonstrate a compact optical fiber microwire current sensor based on the Faraday effect with gigahertz frequency of current sensing capabilities.

We demonstrate broadband supercontinuum generation (SCG) in a dispersion-engineered silicongermanium waveguide. The 3-cm long waveguide is pumped by femtosecond pulses at 2.4µm and the generated supercontinuum extends from 1.45µm to 2.79µm (at the -30-dB point). The broadening is mainly driven by the generation of a dispersive wave in the 1.5-1.8µm region and soliton fission. The SCG was modelled numerically and excellent agreement with the experimental results was obtained. © Silicon (Si) photonics has witnessed rapid maturity in recent years, mainly due to its potential for high-yield, low-cost CMOS-compatible fabrication of components. At the same time, the high nonlinear refractive index of silicon (n 2 = 4.5x10 −18 m 2 /W), especially when combined with small-dimension, high refractive-index-contrast waveguide geometries that lead to tight mode confinement, makes Si photonic technologies particularly attractive for nonlinear applications. Si-based devices have already been utilized to demonstrate numerous all-optical signal processing applications. Indeed, nonlinear effects such as four-wave mixing (FWM) [1], self-phase modulation (SPM) [2] and Raman amplification [3] have been demonstrated in silicon-on-insulator (SOI) waveguides and nanowires designed for operation in the near-infrared (IR).Silicon is also an excellent candidate for mid-IR applications, due to its transparency up to 8µm and to the reduced two-photon and free-carrier absorptions at wavelengths beyond 2.2µm. Leveraging on these attributes, moderate to high brightness wide-bandwidth laser sources have been demonstrated based on supercontinuum generation (SCG) in this wavelength region, using waveguides fabricated on either crystalline silicon [4,5], amorphous silicon [6] or silicon nitride [7]. Furthermore, the development of on-chip sources providing short pulses has driven research towards integrating both the pump source and nonlinear element on the same chip [8].We have recently reported the first demonstrations of alloptical signal processing using silicon germanium waveguides both in the near-[9] and mid-IR [10]. These demonstrations, along with a detailed study on the optical properties of SiGe waveguides [11], have highlighted that the addition of germanium to silicon can enhance the nonlinear response in comparison to pure silicon, as well as act as an additional valuable design parameter that can impact a host of optical properties (such as linear loss, two-photon absorption (TPA) and dispersion) of the nonlinear waveguide.In this Letter, we have extended the work presented in [12] where we reported the generation of a broadband supercontinuum (SC) in a dispersion-engineered SiGe waveguide. The waveguide was pumped using femtosecond pump pulses at 2.4µm and the 30-dB bandwidth of the SC extended more than 1330 nm spanning both the mid-IR and the entire telecommunication wavelength window, while maintaining high spectral uniformity. A numerical model was also developed to study the SCG, providing excellent agreement with the exper...

Abstract-A review of passive components based on optical microfibers is presented.