The effects of temperature on the Brillouin spectrum in novel carbon/polyimide coated fibers have been firstly studied.
We also firstly investigated the aging behavior for these fibers by comparing the changing of the relationship between
Brillouin frequency shift and temperature.
Directly modulated lasers (DML) have been widely used in data rate at 2.5 Gb/s and below. The advantages of
its simplicity and cost effectiveness have attracted considerable amount of effort in developing DMLs for higher data
rate optical transmission systems, especially for short reach applications. The major issue is semiconductor laser's
intrinsic modulation bandwidth and the amplitude modulation induced frequency chirp at high speed of 10 Gb/s and
beyond. In this paper, we first briefly review the advancement of directly modulated lasers at 10 Gb/s and above. We
then present our work on the investigation of using 10 Gb/s directly modulated laser in multiple amplified spans of a
typical metro system. The experimental results show that 10 Gb/s DML may have potential to be a cost-effective option
for a typical 100GHz spacing DWDM, 6x80km metro link over standard single-mode fiber. The DML performance will
also be compared to conventional Mach-Zehnder modulator-based transmitter.
Distributed Raman amplification in the transmission fiber is an important technology for advancing the system performance. Co-directionally pumped Raman amplifiers can enhance the performance and allow more flexibility in the system design. However, several sources of non-amplified spontaneous emission noise need to be carefully considered in the amplifier design. The intrinsic cross gain modulation associated with the transient nature of Raman effect can impair the system performance, if the amplifier is not properly designed. We have isolated and measured the impairment due to cross gain modulation in 200-km bi-directionally pumped fiber spans. The penalty depends on the fiber dispersion characteristics and can be small for up to 20 dB on-off co-gain. The benefit of co-directionally pumped Raman amplifiers can be used in multiple long-span transmission to compensate the high loss while maintaining a low nonlinear impairment. It can also be used to extend the length of a single span and achieve a simple system configuration for unrepeatered applications. As opposed to using a span containing multiple fiber types and remotely pumped erbium-doped fiber amplification to achieve transmission over spans with > 60 dB loss, we have demonstrated an unrepeatered link over a single type of fiber with bi-directional Raman pumping. Using the simple conventional non-return-to-zero data format, we achieved transmission of 20 × 10Gb/s channels over a 300-km span of non-zero dispersion-shifted fiber. This simple system configuration provides an important option for terrestrial transmission in remote areas where service access is difficult.
A conventional SMF-28 was used to conduct localized pipe-wall buckling monitoring in a section of energy pipe with 2,667 mm (105 in) in length and 762 mm (30 in) in diameter by a coherent probe-pump based distributed Brillouin fiber sensor with 15 cm spatial resolution. The locations of pipe-wall buckling have been found by measuring the strain distributions along the outer surface of the pipe. However the sensing fiber (SMF-28) was broken when the bending load increased above 1335 kN (300 kips), which caused the sensing fiber experienced more than the compressive strains of -8,084 με. In order to get strain data after pipeline buckling happens, a high strength sensing fiber with carbon coating instead of conventional acrylate coating should be used. The Brillouin measurement on the carbon coating single-mode fiber has Brillouin frequency shift of vB 12.479 GHz at wavelength of 1320 nm and room temperature. The measured Brillouin bandwidth ΔvB is equal to 66 MHz. The central Brillouin frequency shows a strong dependence on strain with 1.510 GHz shift at 2.5% elongation. The excellent linearity of the central frequency vB on strain is confirmed and the strain coefficient was measured as 16.21 με/MHz. Its strain-stress relation keeps linearity up to 2.5% elongation, which is much bigger than that of SMF-28.
C-phycocyanin (CPC) and Allophycocyanin (APC) are pigment-protein complexes isolated from antenna systems in cyanobacteria. The crystal structure of CPC has recently been solved and APC has a similar structure. CPC and APC have a trimeric structure, monomeric subunits are composed of an (alpha) and (beta) polypeptide chain, each has a tetrapyrrole chromophore chemically bound to position 84. In CPC and APC trimers, the (alpha) 84 and (beta) 84 chromophores in adjacent monomers are in close proximity, forming relatively strong coupled pairs. Calculation of pairwise energy transfer rates using Foerster theory has suggested an extremely fast transfer (> 1 ps-1) between the (alpha) 84 and (beta) 84 pair in CPC. A femtosecond fluorescence up-conversion apparatus was constructed which achieves subhundred femtosecond time resolution. This allows experimental observation of the fast energy transfer process between the (alpha) 84 and (beta) 84 pair in both CPC and APC. There was also a wavelength dependence of the fluorescence depolarization kinetics which is inconsistent with Foerster inductive resonance energy transfer theory.
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