Linear semiconductor optical amplifiers

The chapter reviews properties and applications of linear semiconductor optical amplifiers (SOA). Section 12.1 covers SOA basics, including working principles, material systems, structures and their growth. Booster or inline amplifiers as well as low-noise preamplifiers are classified. Section 12.2 discusses the influence of parameters like gain, noise figure, gain saturation, gain and phase dynamics, and alpha-factor. In Sect. 12.3, the application of a linear SOA as a reach extender in future access networks is addressed. The input power dynamic range is introduced, and measurements for on-off keying and phase shift keying signals are shown. Section 12.4 presents the state of the art for commercially available SOA and includes a treatment of reflective SOAs (RSOA) as well. © 2012 Springer-Verlag Berlin Heidelberg.

Short-term in vitro responses of human peripheral blood monocytes to ferritic stainless steel fiber networks.

Beneficial effects on bone-implant bonding may accrue from ferromagnetic fiber networks on implants which can deform in vivo inducing controlled levels of mechanical strain directly in growing bone. This approach requires ferromagnetic fibers that can be implanted in vivo without stimulating undue inflammatory cell responses or cytotoxicity. This study examines the short-term in vitro responses, including attachment, viability, and inflammatory stimulation, of human peripheral blood monocytes to 444 ferritic stainless steel fiber networks. Two types of 444 networks, differing in fiber cross section and thus surface area, were considered alongside austenitic stainless steel fiber networks, made of 316L, a widely established implant material. Similar high percent seeding efficiencies were measured by CyQuant® on all fiber networks after 48 h of cell culture. Extensive cell attachment was confirmed by fluorescence and scanning electron microscopy, which showed round monocytes attached at various depths into the fiber networks. Medium concentrations of lactate dehydrogenase (LDH) and tumor necrosis factor alpha (TNF-α) were determined as indicators of viability and inflammatory responses, respectively. Percent LDH concentrations were similar for both 444 fiber networks at all time points, whereas significantly lower than those of 316L control networks at 24 h. All networks elicited low-level secretions of TNF-α, which were significantly lower than that of the positive control wells containing zymosan. Collectively, the results indicate that 444 networks produce comparable responses to medical implant grade 316L networks and are able to support human peripheral blood monocytes in short-term in vitro cultures without inducing significant inflammatory or cytotoxic effects.

74-fs nanotube-mode-locked fiber laser

We report an erbium-doped, nanotube mode-locked fiber oscillator generating 74 fs pulses with 63 nm spectral width. This all-fiber-based laser is a simple, low-cost source for time-resolved optical spectroscopy, as well as for many applications where high resolution driven by short pulse durations is required. © 2012 American Institute of Physics.

In vitro osteoblast response to ferritic stainless steel fiber networks for magneto-active layers on implants

The use of a porous coating on prosthetic components to encourage bone ingrowth is an important way of improving uncemented implant fixation. Enhanced fixation may be achieved by the use of porous magneto-active layers on the surface of prosthetic implants, which would deform elastically on application of a magnetic field, generating internal stresses within the in-growing bone. This approach requires a ferromagnetic material able to support osteoblast attachment, proliferation, differentiation, and mineralization. In this study, the human osteoblast responses to ferromagnetic 444 stainless steel networks were considered alongside those to nonmagnetic 316L (medical grade) stainless steel networks. While both networks had similar porosities, 444 networks were made from coarser fibers, resulting in larger inter-fiber spaces. The networks were analyzed for cell morphology, distribution, proliferation, and differentiation, extracellular matrix production and the formation of mineralized nodules. Cell culture was performed in both the presence of osteogenic supplements, to encourage cell differentiation, and in their absence. It was found that fiber size affected osteoblast morphology, cytoskeleton organization and proliferation at the early stages of culture. The larger inter-fiber spaces in the 444 networks resulted in better spatial distribution of the extracellular matrix. The addition of osteogenic supplements enhanced cell differentiation and reduced cell proliferation thereby preventing the differences in proliferation observed in the absence of osteogenic supplements. The results demonstrated that 444 networks elicited favorable responses from human osteoblasts, and thus show potential for use as magnetically active porous coatings for advanced bone implant applications. © 2012 Wiley Periodicals, Inc.

Tm-doped fiber laser mode-locked by graphene-polymer composite

We demonstrate mode-locking of a thulium-doped fiber laser operating at 1.94 μm, using a graphene-polymer based saturable absorber. The laser outputs 3.6 ps pulses, with ∼0.4 nJ energy and an amplitude fluctuation ∼0.5%, at 6.46 MHz. This is a simple, low-cost, stable and convenient laser oscillator for applications where eye-safe and low-photon-energy light sources are required, such as sensing and biomedical diagnostics. © 2012 Optical Society of America.

Coexistence of high-bit-rate quantum key distribution and data on optical fiber

Quantum key distribution (QKD) uniquely allows distribution of cryptographic keys with security verified by quantum mechanical limits. Both protocol execution and subsequent applications require the assistance of classical data communication channels. While using separate fibers is one option, it is economically more viable if data and quantum signals are simultaneously transmitted through a single fiber. However, noise-photon contamination arising from the intense data signal has severely restricted both the QKD distances and secure key rates. Here, we exploit a novel temporal-filtering effect for noise-photon rejection. This allows high-bit-rate QKD over fibers up to 90 km in length and populated with error-free bidirectional Gb/s data communications. With high-bit rate and range sufficient for important information infrastructures, such as smart cities and 10 Gbit Ethernet, QKD is a significant step closer towards wide-scale deployment in fiber networks.

Double-wall carbon nanotube Q-switched and mode-locked two-micron fiber lasers

We fabricate double-wall carbon nanotube polymer composite saturable absorbers and demonstrate stable Q-switched and Mode-locked Thulium fiber lasers in a linear cavity and a ring cavity respectively. © 2012 OSA.

Graphene passively Q-switched two-micron fiber lasers

We demonstrate a passively Q-switched thulium fiber laser, using a graphene-based saturable absorber. The laser is based on an all-fiber ring cavity and produces ∼2.3 μs pulses at 1884nm, with a maximum pulse energy of 70 nJ. © 2012 OSA.

Mode-locking by nanotubes of a Raman laser based on a highly doped GeO 2 fiber

A mode-locked Raman laser, using 25 m of a GeO2 doped fiber as the gain medium, is reported employing carbon nanotubes. The oscillator generates 850 ps chirped pulses, which are externally compressed to 185 ps. © 2012 OSA.

Pulsewidth switchable, wavelength tuneable ultrafast fiber laser mode-locked by carbon nanotubes

Employing a nanotube-based saturable absorber, we demonstrate a continuously tunable (1533-1563nm) ultrafast fiber laser, with output pulsewidth switchable between picosecond (1.2 ps) and femtosecond (610 fs) regimes. © 2012 IEEE.

Dual-wavelength, carbon nanotube mode-locked fiber laser

We demonstrate a dual-wavelength, carbon nanotube mode-locked Er fiber laser. The laser outputs two wavelengths at 1549nm and 1562nm, and each wavelength corresponds to pulse duration of ∼1.3ps and repetition rate of ∼11.27MHz. © 2012 IEEE.

Mechanical response of carbon fiber composite sandwich panels with pyramidal truss cores

The combination of light carbon fiber reinforced polymer (CFRP) composite materials with structurally efficient sandwich panel designs offers novel opportunities for ultralight structures. Here, pyramidal truss sandwich cores with relative densities ρ̄ in the range 1-10% have been manufactured from carbon fiber reinforced polymer laminates by employing a snap-fitting method. The measured quasi-static shear strength varied between 0.8 and 7.5 MPa. Two failure modes were observed: (i) Euler buckling of the struts and (ii) delamination failure of the laminates. Micro-buckling failure of the struts was not observed in the experiments reported here while Euler buckling and delamination failures occurred for the low (ρ̄≤1%) and high (ρ̄>1%) relative density cores, respectively. Analytical models for the collapse of the composite cores by these failure modes are presented. Good agreement between the measurements and predictions based on the Euler buckling and delamination failure of the struts is observed while the micro-buckling analysis over-predicts the measurements. The CFRP pyramidal cores investigated here have a similar mechanical performance to CFRP honeycombs. Thus, for a range of multi-functional applications that require an "open-celled" architecture (e.g. so that cooling fluid can pass through a sandwich core), the CFRP pyramidal cores offer an attractive alternative to honeycombs. © 2012 Elsevier Ltd. All rights reserved.