The steady performance of a porous and compliant aerostatic thrust bearing

Recent developments in aerostatic thrust bearings have included: (a) the porous aerostatic thrust bearing containing a porous pad and (b) the inherently compensated compliant surface aerostatic thrust bearing containing a thin elastomer layer. Both these developments have been reported to improve the bearing load capacity compared to conventional aerostatic thrust bearings with rigid surfaces. This development is carried one stage further in a porous and compliant aerostatic thrust bearing incorporating both a porous pad and an opposing compliant surface. The thin elastomer layer forming the compliant surface is bonded to a rigid backing and is of a soft rubber like material. Such a bearing is studied experimentally and theoretically under steady state operating conditions. A mathematical model is presented to predict the bearing performance. In this model is a simplified solution to the elasticity equations for deflections of the compliant surface. Account is also taken of deflections in the porous pad due to the pressure difference across its thickness. The lubrication equations for flow in the porous pad and bearing clearance are solved by numerical finite difference methods. An iteration procedure is used to couple deflections of the compliant surface and porous pad with solutions to the lubrication equations. Comparisons between experimental results and theoretically predicted bearing performance are in good agreement. However these results show that the porous and compliant aerostatic thrust bearing performance is lower than that of a porous aerostatic thrust bearing with a rigid surface in place of the compliant surface. This discovery is accounted to the recess formed in the bearing clearance by deflections of the compliant surface and its effect on flow through the porous pad.

Optical data transmission using periodic in-line all-optical format conversion

We introduce a novel transmission technique of periodic in-line all-optical format conversion between return-to-zero and non-return-to-zero-like aimed at delaying the accumulation of format-specific impairments. A particular realization of this approach using in-line normal dispersion fibre-enhanced nonlinear optical loop mirrors at 40Gbit/s data rate is presented. © 2004 Optical Society of America.

Optical data transmission using periodic in-line all-optical format conversion

We introduce a novel transmission technique of periodic in-line all-optical format conversion between return-to-zero and non-return-to-zero-like aimed at delaying the accumulation of format-specific impairments. A particular realization of this approach using in-line normal dispersion fibre-enhanced nonlinear optical loop mirrors at 40Gbit/s data rate is presented.

All-optical 42.6 Gbit/s NRZ to RZ format conversion by cross-phase modulation in single SOA

A 42.6 Gbit/s all-optical non-retum-to-zero (NRZ) to return-to-zero (RZ) format converter using a single SOA followed by an asymmetrical Mach-Zehnder interferometer is presented. The format converter generates a correctly-coded RZ signal with a controllable duty-cycle. It has the advantages of flexible input N RZ wavelength, preserved input polarity, negative bit error rate power penalty and low switching pulse energy (15fJ).

Simultaneous multiple channel all-optical NRZ to CSRZ and RZ to CSRZ format conversion using an SOA-NOLM

The optical conversion bandwidth for an all-optical modulation format converter, based on a semiconductor laser amplifier in a nonlinear optical loop mirror (SOA-NOLM), is investigated. 4 Â 10 Gbit/s channels are all- optically converted between both non-return-to-zero (NRZ) and return-to-zero (RZ) format to carrier- suppressed return-to-zero (CSRZ). WDM transmission of the converted signals over a 194 km fibre span is then demonstrated. The receiver sensitivity for the converted four wavelengths is measured and compared after transmission.

Simultaneous multiple channel all-optical NRZ to CSRZ and RZ to CSRZ format conversion using an SOA-NOLM

The optical conversion bandwidth for an all-optical modulation format converter, based on a semiconductor laser amplifier in a nonlinear optical loop mirror (SOA-NOLM), is investigated. 4 Â 10 Gbit/s channels are all- optically converted between both non-return-to-zero (NRZ) and return-to-zero (RZ) format to carrier- suppressed return-to-zero (CSRZ). WDM transmission of the converted signals over a 194 km fibre span is then demonstrated. The receiver sensitivity for the converted four wavelengths is measured and compared after transmission.

Simultaneous multiple channel all-optical NRZ to CSRZ and RZ to CSRZ format conversion using an SOA-NOLM

The optical conversion bandwidth for an all-optical modulation format converter, based on a semiconductor laser amplifier in a nonlinear optical loop mirror (SOA-NOLM), is investigated. 4×10 Gbit/s channels are all-optically converted between both non-return-to-zero (NRZ) and return-to-zero (RZ) format to carrier-suppressed return-to-zero (CSRZ). WDM transmission of the converted signals over a 194 km fibre span is then demonstrated. The receiver sensitivity for the converted four wavelengths is measured and compared after transmission. © 2014 Elsevier B.V. All rights reserved.

Optimally-designed single fiber Bragg grating filter scheme for RZ-OOK/DPSK/DQPSK to NRZ-OOK/DPSK/DQPSK format conversion

We investigate return-to-zero (RZ) to non-return-to-zero (NRZ) format conversion by means of the linear time-invariant system theory. It is shown that the problem of converting random RZ stream to NRZ stream can be reduced to constructing an appropriate transfer function for the linear filter. This approach is then used to propose novel optimally-designed single fiber Bragg grating (FBG) filter scheme for RZ-OOK/DPSK/DQPSK to NRZ-OOK/DPSK/DQPSK format conversion. The spectral response of the FBG is designed according to the optical spectra of the algebraic difference between isolated NRZ and RZ pulses, and the filter order is optimized for the maximum Q-factor of the output NRZ signals. Experimental results as well as simulations show that such an optimallydesigned FBG can successfully perform RZ-OOK/DPSK/DQPSK to NRZOOK/ DPSK/DQPSK format conversion.

CLAE to move to online format

Editorial: The 2015 BCLA annual conference was another fantastic affair. It was the first time the conference was held in the beautiful city of Liverpool. The venue was great and the programme was excellent. The venue overlooked the River Mersey and many of the hotels were local boutique hotels. I stayed in one which was formerly the offices of White Star Liners—where the RMS Titanic was originally registered. The hotel decor was consistent with its historic significance. The BCLA gala dinner was held in the hugely impressive Anglican Cathedral with entertainment from a Beatles tribute band. That will certainly be a hard act to follow at the next conference in 2017. Brian Tompkins took the reigns as the new BCLA president. Professor Fiona Stapleton was the recipient of the BCLA Gold Medal Award. The winner of the poster competition was Dorota Szczesna-Iskander with a poster entitled ‘Dry Contact lens poor wettability and visual performance’. Second place was Renee Reeder with her poster entitled ‘Abnormal Rosacea as a differential diagnosis in corneal scarring’. And third place was Maria Jesus Gonzalez-Garcia with her poster entitled ‘Dry Effect of the Environmental Conditions on Tear Inflammatory Mediators Concentration in Contact Lens Wearers’. The photographic competition winner was Professor Wolfgang Sickenberger from Jena in Germany. The Editorial Panel of CLAE met at the BCLA conference for their first biannual meeting. The journal metrics were discussed. In terms of number of submissions of new papers CLAE seems to have plateaued after seeing a rapid growth in the number of submissions over the last few years. The increase over the last few years could be attributed to the fact that CLAE was awarded an impact factor for the first time in 2012. This year it seems that impact factors across nearly all ophthalmic related journals has dropped. This could in part be due to the fact that last year was a ‘Research Exercise Framework (REF) year for UK universities, where they are judged on quality of their research output. The next REF is in 2020 so we may see changes nearing that time. Looking at article downloads, there seems to be a continued rise in figures. Currently CLAE attracts around 85,000 downloads per year (this is an increase of around 10,000 per year for the last few years) and the 2015 prediction is 120,000! With this in mind and with other contributing factors too, the BCLA has decided to move to online delivery of CLAE to its members starting from issue 5 of 2015. Some members do like to flick through the pages of a hard copy of the journal so members will still have the option of receiving a hard copy through the post but the default journal delivery method will now be online. The BCLA office will send various alerts and content details to members email addresses. To access CLAE online you will need to log in via the BCLA web page, currently you then click on ‘Resources’ and then under ‘Free and Discounted Publications’ you will see CLAE. This actually takes you to CLAE’s own webpage (www.contactlensjournal.com) but you need to log in via the BCLA web page. The BCLA plans to change these weblinks so that from the BCLA web page you can link to the journal website much more easily and you have the choice of going directly into the general website for CLAE or straight to the current issue. In 2016 you will see an even easier way of accessing CLAE online as the BCLA will launch a CLAE application for mobile devices where the journal can be downloaded as a ‘flick-book’. This is a great way of bringing CLAE into the modern era where people access their information in newer ways. For many the BCLA conference was part of a very busy conference week as it was preceded by the International Association of Contact Lens Educators’ (IACLE) Third World Congress, held in Manchester on the 4 days before the BCLA conference. The first and second IACE World Congresses were held in Waterloo, Canada in 1994 and 2000 respectively and hosted by Professor Des Fonn. Professor Fonn was the recipient of the first ever IACLE lifetime achievement award. The Third IACLE World Congress saw more than 100 contact lens educators and industry representatives from around 30 countries gather in the UK for the four-day event, hosted by The University of Manchester. Delegates gained hands-on experience of innovations in teaching, such as learning delivery systems, the use of iPads in the classroom and for creating ePub content, and augmented and virtual reality technologies. IACLE members around the world also took part via a live online broadcast. The Third IACLE World Congress was made possible by the generous support of Sponsors Alcon, CooperVision and Johnson & Johnson Vision Care., for more information look at the IACLE web page (www.iacle.org).

Simultaneous multichannel carrier-suppressed return-to-zero to non-return-to-zero format conversion using a fiber Bragg grating

A novel multichannel carrier-suppressed return-to-zero (CSRZ) to non-return-to-zero (NRZ) format conversion scheme based on a single custom-designed fiber Bragg grating (FBG) with comb spectra is proposed. The spectral response of each channel is designed according to the algebraic difference between the CSRZ and NRZ spectra outlines. The tailored group delays are introduced to minimize the maximum refractive index modulation. Numerical results show that four-channel 200-GHz-spaced CSRZ signals at 40 Gbits/s can be converted into NRZ signals with high Q-factor and wide-range robustness. It is shown that our proposed FBG is robust to deviations of bandwidth and central wavelength detuning. Another important merit of this scheme is that the pattern effects are efficiently reduced owing to the well-designed spectra response.