Publications (193)179.82 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: We present a novel method to validate the relative amount of power carried by high order modes in a multimode fiber using a Spatial and Spectral (S2) imaging technique. The method can be utilized to calibrate the S2 set-up and uses Fresnel reflections from a thin glass plate to compare theoretical values with experimental results. We have found that, in the most general case, spectral leakage and sampling errors can lead S2 to underestimate the multipath interference (MPI) of high order modes by several decibels, thus significantly impairing the result of the measurement. On the other hand, by applying suitable corrections as described in this work, we demonstrate that the S2 produces MPI estimates that are accurate to within 1dB or better.
- [Show abstract] [Hide abstract] ABSTRACT: The 2-μm wave band is emerging as a potential new window for optical telecommunications with several distinct advantages over the traditional 1.55 μm region. First of all, the hollow-core photonic band gap fiber (HC-PBGF) is an emerging transmission fiber candidate with ultra-low nonlinearity and lowest latency (0.3% slower than light propagating in vacuum) that has its minimum loss within the 2-μm wavelength band. Second, the thulium-doped fiber amplifier that operates in this spectral region provides significantly more bandwidth than the erbium-doped fiber amplifier. In this paper, we demonstrate a single-channel 2-μm transmitter capable of delivering >52 Gbit/s data signals, which is twice the capacity previously demonstrated. To achieve this, we employ discrete multitone modulation via direct current modulation of a Fabry–Perot semiconductor laser. The 4.4-GHz modulation bandwidth of the laser is enhanced by optical injection locking, providing up to 11 GHz modulation bandwidth. Transmission over 500-m and 3.8-km samples of HC-PBGF is demonstrated.
- [Show abstract] [Hide abstract] ABSTRACT: We present a novel method for validating the relative power value (MPI) of the Spatial and Spectral (S2) imaging technique. By applying corrections for spectral leakage and sampling errors we found the MPI determinations to be accurate within 1dB.
- [Show abstract] [Hide abstract] ABSTRACT: We report the fabrication of a record 11km length of photonic bandgap fiber supporting >200nm bandwidth with longitudinally uniform loss of ≈5dB/km at 1560nm and demonstrate error-free, low-latency, direct-detection 10Gbit/s transmission across the entire C-Band.
- [Show abstract] [Hide abstract] ABSTRACT: Optical injection locking is used to increase the modulation bandwidth and suppress chirp in a single-channel, single-polarization discrete multi-tone bit-loading-optimized transmitter. Transmission through a hollow-core photonic bandgap fiber with negligible signal degradation and distortion is demonstrated.
- [Show abstract] [Hide abstract] ABSTRACT: We show for the first time 100 Gbit/s total capacity at 2 µm waveband, using 4 × 9.3 Gbit/s 4-ASK Fast-OFDM direct modulation and 4 × 15.7 Gbit/s NRZ-OOK external modulation, spanning a 36.3 nm wide wavelength range. WDM transmission was successfully demonstrated over 1.15 km of low-loss hollow core photonic bandgap fiber (HC-PBGF) and over 1 km of solid core fiber (SCF). We conclude that the OSNR penalty associated with the SCF is minimal, while a ~1-2 dB penalty was observed after the HC-PBGF probably due to mode coupling to higher-order modes.
- [Show abstract] [Hide abstract] ABSTRACT: We present for the first time the group velocity dispersion of multiple distinguishable modes propagating in 3, 7 and 19 cell hollow core photonic bandgap fibres. Measurements are made by direct phase extraction from spectral domain low coherence interferometry.
- [Show abstract] [Hide abstract] ABSTRACT: We report on the use of novel low loss Hollow Core Photonic Bandgap Fibres (HC-PBGFs) operating in the mid-IR for broadband absorption measurements of low-level concentrations of Acetylene and Ethane gas around 3 and 3.3 μm, respectively. The availability of improved HC-PBGFs operating in the 3-3.6 mm wavelength range with ∼0.05-0.1 dB/m loss enables accessing the strongest fundamental ro-vibrational bands (e.g. C-H, O-H, N-H), thus opening up the possibility of absorption based gas sensing with much higher sensitivity than has been demonstrated to date utilizing fibres optimized for near-IR operation. We present for the first time spectroscopic absorption measurements of C2H2 at ∼3.05 μm (2.5 vol% concentration) and of C2H6 at 3.35 μm (50 ppmV concentration) using HC-PBGF cells. Results indicate that sub-ppm sensitivities can easily be achieved using fiber lengths of a few meters and simple detection schemes.
- [Show abstract] [Hide abstract] ABSTRACT: A differential profilometry technique is adapted to the problem of measuring the roughness of hollow glass fibres by use of immersion objectives and index-matching liquid. The technique can achieve picometer level sensitivity. Cross validation with AFM measurements is obtained through use of vitreous silica step calibration samples. Measurements on the inner surfaces of fibre-sized glass capillaries drawn from high purity suprasil F300 tubes show a sub-nanometer roughness, and the roughness power spectrum measured in the range [5·10−3μm−1 − 10−1μm−1] is consistent with the description of the glass surface as a superposition of frozen capillary waves. The surface roughness spectrum of two capillary tubes of differing compositions can be quantitatively distinguished.
- [Show abstract] [Hide abstract] ABSTRACT: We report a novel OFDM-transmitter operating in the emerging 2-μm waveband. Sub-FEC limit transmission of a 32QAM signal over 500m of both solid and hollow-core fiber was achieved and the generation of 30Gbits 64QAM demonstrated.
- [Show abstract] [Hide abstract] ABSTRACT: X-ray computational tomography is demonstrated as a powerful non-destructive tool to image the internal structure of a hollow core photonic band-gap fibre and its preforms. The technique is applied to measure the deformation within a splice with unprecedented detail.
- [Show abstract] [Hide abstract] ABSTRACT: We review our recent progress in developing hollow core photonic bandgap fibers for high capacity data transmission. Novel numerical and characterization tools developed to improve fiber performance and yield will be discussed.
- [Show abstract] [Hide abstract] ABSTRACT: Specialty optical fibers, in particular microstructured and multi-material optical fibers, have complex geometry in terms of structure and/or material composition. Their fabrication, although rapidly developing, is still at a very early stage of development compared with conventional optical fibers. Structural characterization of these fibers during every step of their multi-stage fabrication process is paramount to optimize the fiber-drawing process. The complexity of these fibers restricts the use of conventional refractometry and microscopy techniques to determine their structural and material composition. Here we present, to the best of our knowledge, the first nondestructive structural and material investigation of specialty optical fibers using X-ray computed tomography (CT) methods, not achievable using other techniques. Recent advances in X-ray CT techniques allow the examination of optical fibers and their preforms with sub-micron resolution while preserving the specimen for onward processing and use. In this work, we study some of the most challenging specialty optical fibers and their preforms. We analyze a hollow core photonic band gap fiber and its preforms, and bond quality at the joint between two fusion-spliced hollow core fibers. Additionally, we studied a multi-element optical fiber and a metal incorporated dual suspended-core optical fiber. The application of X-ray CT can be extended to almost all optical fiber types, preforms and devices.
Conference Paper: X-ray computational tomography of hollow core photonic bandgap fibre
- [Show abstract] [Hide abstract] ABSTRACT: A method to track the evolution of a microstructured fibre, from initial preform to final fibre geometry, is presented. Up scaling to longer lengths, new structure development and effects of material parameters can all be explored with this model.
Conference Paper: Towards real-time mode content characterization of multimode fibers[Show abstract] [Hide abstract] ABSTRACT: We present a new S2-based technique with potential for near real-time (1s) characterization of the modal-content of multimode fibers. We also demonstrate the identification and removal of measurement artifacts originating from reflections from optical components.
- [Show abstract] [Hide abstract] ABSTRACT: This paper presents WDM transmission at 2μm over 1.15km of HC-PBGF with wavelength channels selected to span a 36.3nm waveband. A total capacity of 81Gbit/s was achieved using 4×12.5Gbit/s NRZ-OOK external modulation and 4×7.7Gbit/s 4-ASK Fast-OFDM direct modulation signals.
- [Show abstract] [Hide abstract] ABSTRACT: A photonic integrated mode coupler based on silicon-on-insulator is employed for mode division multiplexing (MDM) over a 193 m 19-cell hollow-core photonic bandgap fibre (HC-PBGF) with a -3 dB bandwidth > 120 nm. Robust MDM transmissions using LP01 and LP11 modes, and two degenerate LP11 modes (LP11a and LP11b) are both experimentally verified.
University of Southampton
Southampton, England, United Kingdom
- Optoelectronics Research Centre (ORC)
BAE SystemsLondinium, England, United Kingdom