Microstructured cladding elements to enhance performance and flexibility of large mode area leakage channel fibers

Large mode area fibers are imperative for scaling up the average power of fiber lasers. Single-mode behavior and low FM loss are the crucial functionalities for these fibers. However, for key applications such as picosecond pulsed lasers, the device length needs to at least a few meters. This makes a certain degree of bend tolerance a prerequisite in the fiber design. While rod-type PCFs have been very successful in offering large mode areas, their rigid configuration limits their application domain. Alternatively, leakage channel fibers (LCFs) have shown a great potential for offering substantial bend tolerance along with large mode areas. However, the proposed use of Fluorine-doped rods in the all-solid version limits their practical design space. Here, we propose a novel design concept to attain single-material, large mode area fibers (mode area >~ 1000µm2) with effectively single mode operation coupled with bending characteristics comparable to all-solid LCFs and greater design flexibility and easier splicing that is comparable to rod-type PCFs

Predicting Structural and Optical Properties of Hollow-Core Photonic Bandgap Fibers from Second Stage Preforms

We propose a simple theory based on mass conservation that allows accurate prediction of guidance properties in hollow-core photonic bandgap fibers (HC-PBGF) from knowledge of the second stage preforms from which the fibers are drawn

An Innovative On-Board Processor for Lightsats

The Applied Physics Laboratory has developed a flightworthy custom microprocessor that increases capability and reduces development costs of lightsat science instruments. This device, which APL calls the FRISC (Forth Reduced Instruction Set Computer), directly executes the high level language called Forth, which is ideally suited to the multitasking control and data processing environment of a spaceborne instrument processor. The FRlSC (which is available commercially as the SC32) will be flown as the on-board processor in the Magnetic Field Experiment on the Swedish Space Corporations’ Freja satellite. APL has achieved a significant increase in on-board processing capability with no increase in cost when compared to the magnetometer instrument on Freja\u27s predecessor, the Viking satellite. These advantages are attributable to the high instruction execution rate, reduced software development effort, and shortened system integration time made possible by the nature of the microprocessor and the Forth language

Manufacturing of high performance hollow core microstructured optical fibres

Although fabrication technologies of Microstructured Optical Fibres (MOFs) fibres have matured at an impressive rate over the past ten years, these fibres are widely perceived as "challenging" and some key issues are still outstanding in order to improve their manufacturability. One such issue revolves around methods to improve structural control during the fibre draw. Structural control is of particular importance for certain types of microstructured fibres, such as hollow core Photonic Bandgap Fibres (PBGFs) and Anti-resonant (AR) fibres (also known as Kagome fibres). These fibres exploit resonant and/or anti-resonant guidance mechanisms and thus their transmission properties depend on the structure to a much greater extent as compared to conventional fibres. Hollow core MOFs have been identified as promising media for applications such as low latency (speed-of-light-in-air) communications, fibre sensing (chemical sensing, gyroscopes, sensors based on distributed scattering), laser power delivery (both high-peak and high average). However the successful implementation of these fibres in advanced demonstrators leading to commercial devices has been hindered by high cost, poor consistency and, in some instances, by lack of fibres with sufficiently good properties. We are actively investigating methods to improve structural control during the fibre draw and methods for scaling up the current manufacturing yields. Here we present recent progress in the fabrication hollow core MOFs at the Optoelectronics Research Centre; in particular, we report the fabrication of ultra-low loss (~few dB/km), wide bandwidth (>150nm) Photonic Bandgap Fibres and anti-resonant Hexagram Fibres with broadband low loss transmission suitable for the delivery of extremely high peak optical powers

Understanding wavelength scaling in 19-cell core hollow-core photonic bandgap fibers

First experimental wavelength scaling in 19-cell core HC-PBGF indicates that the minimum loss waveband occurs at longer wavelengths than previously predicted. Record low loss (2.5dB/km) fibers operating around 2µm and gas-purging experiments are also reported

Entropy and equilibrium state of free market models

Many recent models of trade dynamics use the simple idea of wealth exchanges among economic agents in order to obtain a stable or equilibrium distribution of wealth among the agents. In particular, a plain analogy compares the wealth in a society with the energy in a physical system, and the trade between agents to the energy exchange between molecules during collisions. In physical systems, the energy exchange among molecules leads to a state of equipartition of the energy and to an equilibrium situation where the entropy is a maximum. On the other hand, in the majority of exchange models, the system converges to a very unequal condensed state, where one or a few agents concentrate all the wealth of the society while the wide majority of agents shares zero or almost zero fraction of the wealth. So, in those economic systems a minimum entropy state is attained. We propose here an analytical model where we investigate the effects of a particular class of economic exchanges that minimize the entropy. By solving the model we discuss the conditions that can drive the system to a state of minimum entropy, as well as the mechanisms to recover a kind of equipartition of wealth

1.45 Tbit/s low latency data transmission through 19-cell hollow core photonic band gap fibre

We report transmission of 37 x 40 Gbit/s C-band channels over 250 m of hollow core band gap fibre, at 99.7% the speed of light in vacuum. BER penalty below 1 dB as compared to back-to-back was measured across the C-band

Low loss, tightly coilable, hollow core photonic bandgap fibers for mid-IR applications

We describe low loss (50dB/km at 3.3µm) and low bend sensitivity mid-IR hollow core-photonic bandgap fiber. Gas sensing applications are highlighted by a methane spectrum recorded in our fiber

Hollow core photonic bandgap fibers for mid-IR applications

We review our fabrication of low loss (50dB/km at 3.3µm) and low bend sensitivity HC-PBGFs for mid-IR operation. Gas sensing applications are highlighted by a high resolution methane spectrum recorded in 1.26m of gas-filled fibe

Towards manufacture of ultralow loss hollow core photonic bandgap fiber

Hollow core photonic bandgap fibers (HC-PBGFs) are a class of optical fibers which guide light in a low index core region surrounded by a triangular lattice of air holes separated by a delicate silica web. The precise nature of this cladding structure requires extremely fine control of the fabrication parameters. While HC-PBGFs have found wide range of exciting research applications the initially anticipated potential for ultralow loss below that of single mode fiber (SMF) has yet to be realized. To date loss figures as low as 1.7 dB/km have been reported, however surface roughness at the core cladding interface limited further loss reduction. The loss of HC-PBGFs can potentially be decreased further by increasing the core dimensions and through optimisation of the fabrication process. To date, the manufacture of HC-PBGFs is reliant upon the two stage stack and draw process. To target ultralow loss below what has been reported to date it has become necessary to ensure repeatability and uniformity in the labor intensive stack and draw process. Repeatability is ensured through rigorous cleanliness throughout preform preparation and by precise fabrication control at each stage of manufacture. Figure 1. a) Scanning electron micrograph of a 19 cell core defect HC-PBGF, b) Attenuation scaling of the photonic bandgap (PBG) versus central guidance wavelength of 19 cell core defect HC-PBGF.Greater than 1 km lengths of HC-PBGF (Fig. 1a) can now be drawn with typical attenuations of the order of 2-3 dB/km and with significantly improved optical bandwidth (~ 100 nm) compared with previously reported. These developments open up HC-PBGF for a range of applications such as telecommunications, laser power delivery, gas sensing and strong light matter interactions, for which they have a clear advantage over conventional fibers. The attenuation scaling of the photonic bandgap (PBG) (solid curves) with central operating wavelength has been investigated in 19 cell core defect fibres (Fig. 1b). The expected attenuation proportional to lambda[-3] relationship (dashed red curve) is observed until the infrared absorption edge of silica (black dot dash curve) is breached and the attenuation increases (green curve). Through strategic fabrication improvements we have achieved repeatable low loss manufacture of HC-PBGFs. Future developments in fabrication control and fiber design will allow the realization of ultralow loss HC-PBGF