Picosecond soliton propagation using nonlinear optical loop mirrors as intensity filters

The authors show that by inserting nonlinear optical loop mirrors into an optical fibre transmission line, 1.5 ps solitons may be transmitted over at least 750 km, with amplifiers spaced at 15 km intervals.

Picosecond soliton transmission using concatenated nonlinear optical loop-mirror intensity filters

The issues involved in employing nonlinear optical loop mirrors (NOLMs) as intensity filters in picosecond soliton transmission were examined in detail. It was shown that inserting NOLMs into a periodically amplified transmission line allowed picosecond solitons to be transmitted under conditions considered infeasible until now. The loop mirrors gave dual function, removing low-power background dispersive waves through saturable absorption and applying a negative feedback mechanism to control the amplitude of the solitons. The stochastic characteristics of the pulses that were due to amplifier spontaneous-emission noise were investigated, and a number of new properties were determined. In addition, the mutual interaction between pulses was also significantly different from that observed for longer-duration solitons. The impact of Raman scattering in the computations was included and it was shown that soliton self-frequency shifts may be eliminated by appropriate bandwidth restrictions.

Loan loss provisions, bank valuations and discretion:a comparative study between conventional and Islamic banks

This study investigates the use of reported loan loss provisions (LLP) by investors in their valuations of banks within the Middle East and North Africa region between the years 2006 and 2011. We decompose LLP into discretionary and non-discretionary components to test for differential valuations in the two banking sectors. We use alternative criteria to define the components of LLP in banks: loan quality/size and earnings management/manipulation incentives. We employ a price-level valuation model estimated using two-stage analyses. We find that LLP has positive value relevance to investors in both banking sectors. Investors in Islamic banks price the discretionary component relatively lower than their conventional counterparts. We attribute this result to differences in product and governance structures as well as to the religious perception of Islamic banking. In both banking sectors, investors construe an increase in the non-discretionary component as irrelevant valuation information. Our results are relevant to bank regulators in showing the signalling effect of LLP to bank value and stability. © 2013 Elsevier B.V.

Accounting for derivatives:an evaluation of reporting practice by UK banks

In 1998 the Accounting Standards Board (ASB) published FRS 13, ‘Derivatives and other Financial Instruments: Disclosures’. This laid down the requirements for disclosures of an entity’s policies, objectives and strategies in using financial instruments, their impact on its risk, performance and financial condition, and details of how risks are managed. FRS 13 became effective in March 1999, and this paper uses the 1999 annual reports of UK banks to evaluate the usefulness of disclosures from a user’s perspective. Usefulness is measured in terms of the criteria of materiality, relevance, reliability, comparability and understandability as defined in the ASB’s Statement of Principles (ASB, 1999). Our findings suggest that the narrative disclosures are generic in nature, the numerical data incomplete and not always comparable, and that it is difficult for the user to combine both narrative and numerical information in order to assess the banks’ risk profile. Our overall conclusion is therefore that current UK financial reporting practices are of limited help to users wishing to assess the scale of an institution’s financial risk exposure.

Simple design of FBG-based VSB filters for ultra-dense WDM transmission

A novel approach to ultra-narrow optical vestigial sideband (VSB) filtering based on a specially designed fibre Bragg grating (FBG) operating in transmission is proposed. This design can be easily implemented by writing FBG-based filters for each WDM channel before MUX. The specially designed filter profile allows to take full advantage of crosstalk suppression while minimising waveform distortion.

Reduction of the phase jitter in differential phase-shift-keying soliton transmission systems by in-line Butterworth filters

We examine reduction of phase jitter by use of in-line Butterworth filters in soliton systems in the context of differential phase-shift-keying coding. We also demonstrate numerically that the use of a Butterworth filter in a return-to-zero differential phase-shift-keying system can reduce continuum background radiation.

Market risk reporting by the world's top banks:evidence on the diversity of reporting practice and the implications for international accounting harmonisation

The increasing adoption of international accounting standards and global convergence of accounting regulations is frequently heralded as serving to reduce diversity in financial reporting practice. In a process said to be driven in large part by the interests of international business and global financial markets, one might expect the greatest degree of convergence to be found amongst the world’s largest multinational financial corporations. This paper challenges such claims and presumptions. Its content analysis of longitudinal data for the period 2000-2006 reveals substantial, on going diversity in the market risk disclosure practices, both numerical and narrative, of the world’s top-25 banks. The significance of such findings is reinforced by the sheer scale of the banking sector’s risk exposures that have been subsequently revealed in the current global financial crisis. The variations in disclosure practices documented in the paper apply both across and within national boundaries, leading to a firm conclusion that, at least in terms of market risk reporting, progress towards international harmonisation remains rather more apparent than real.

Design of ultra-narrow WDM filters using the transmission response function of fibre Bragg gratings

We have demonstrated the feasibility of error-free DWDM 8×40 Gb/s transmission over an 800 km SMF/DCF link with 0.8 bit/s/Hz spectral efficiency without polarization multiplexing.

Polarizing fibre Bragg grating filters and its fibre laser application

Poster

Near-constant time delay response of fibre grating Sagnac loop filters

A theoretical and experimental investigation of the time delay characteristics of fiber Bragg grating-based Sagnac loops (FBGSLs) is presented. Analytic expressions for the phase and time delay of the FBGSL have been derived and excellent agreement is found between their predictions and experimental results for configurations incorporating uniform-period and chirped-period gratings. For symmetrical grating structures, it is found that the FBGSL time delay response is similar to that of the incorporated grating; with asymmetrical gratings, the FBGSL response is quite different. It is shown that wavelength-division-multiplexing filters exhibiting near-zero dispersion characteristics can be implemented using FBGSLs.

Direct design of high channel-count fiber Bragg grating filters with low index modulation

A novel method for designing high channel-count fiber Bragg gratings (FBGs) is proposed. For the first time, tailored group delay is introduced into the target reflection spectra to obtain a more even distribution of the refractive index modulation. This approach results in the reduction of the maximum refractive index modulation to physically realizable levels. The maximum index modulation reduction factors are all greater than 5.5. This is a significant improvement compared with previously reported results. Numerical results show that the thus designed high channel-count FBG filters exhibit superior characteristics including 30 dB channel isolation, a flat-top and near 100% reflectivity in each channel. © 2012 Optical Society of America.

Moral hazard, dividends, and risk in banks

In non-financial firms, higher risk taking results in lower dividend payout ratios. In banking, public guarantees may result in a positive relationship between dividend payout ratios and risk taking. I investigate the interplay between dividend payout ratios and bank risk-taking allowing for the effect of charter values and capital adequacy regulation. I find a positive relationship between bank risk-taking and dividend payout ratios. Proximity to the required capital ratio and a high charter value reduce the impact of bank risk-taking on the dividend payout ratio. My results are robust to different proxies for the dividend payout ratio and bank risk-taking. © 2014 John Wiley & Sons Ltd.

Corporate social responsibility and earnings management in U.S. banks

Business decision making depends on financial reporting quality. In identifying the drivers of financial reporting quality, proxied by earnings management (EM), prior literature has drawn attention to the association between corporate EM practices and commitment to corporate social responsibility (CSR). Empirical evidence, however, provides inconclusive results regarding the direction of this association. Using simultaneous equations, we examine the bi-directional CSR-EM relationship in U.S. commercial banks. We demonstrate that, although banks that engage in EM practices are also actively involved in CSR, the reverse relationship is not significant. We provide implications for investors, analysts, business participants and regulators. © 2014 Elsevier Ltd.

Optically tunable fiber grating transmission filters

We propose and demonstrate single- and multiple-passband fiber grating transmission filters that are remotely tunable by exploitation of the optical pump-induced thermal effects in Er Yb-codoped fiber sections. A repeatable, wavelength-independent induced phase shift of 0.1p mW is obtained without hysteresis and anisotropic effects. A transmission extinction ratio of .23 dB with a 3-mW change in pump power is achieved.

Fibre grating filters for suppression of near infrared OH emission lines

Here we present the design and fabrication of multi-notch optical fibre Bragg gratings for suppressing OH emission lines in the near infrared spectra of the night sky for astrophysical applications. We demonstrate a novel approach of fabricating 2, 3 and 5-notch filters using the phase mask technology, which show a good match with the model.