Effect Of Group Delay Ripple Research Articles

Two building blocks of microwave photonics filters in the presence of group delay ripple: a comparative survey

We have developed an analytic approach to investigate the effect of group delay ripple of the dispersive devices on the performance of two major building blocks of microwave-photonic filters. Firstly, performance of PM-based block in the presence of an arbitrary group delay ripple (GDR) is analyzed and compared with the ripple-free case to reveal the destructive effects of added group delay ripple. In the next step, we repeat the proposed approach for the AM-based one; again, the performance is compared with the ripple-free case. Two distortion metrics are also introduced to quantify this distortion. Comparison of the performance of two building blocks in the presence of group delay ripple unveils some interesting characteristics of microwave-photonic filters which have not been mentioned so far. We also add a general survey of two analyzed building blocks to present their respective most significant advantages and shortcomings. The simulated Optisystem results conform to our proposed analytical approach and verify the theoretical model.

Effects of group delay ripple on optical beam-formers for pulsed antenna arrays

A semi-analytical formulation is presented to quantify the effects of group delay ripple on the performance of an optical beam-former. For delay elements, implemented with commercially available multi-channel fiber Bragg gratings, an impulse response is introduced and calculated for the group delay ripple. To do this, the transfer function of the fiber Bragg grating is parted into two dispersive and non-dispersive sections. This will also ease the demonstration of the fiber Bragg grating as a true time delay element. The formulation is applied to an ultra-wideband pulsed array of antennas. As an example the array factor and electric field patterns of a four element antenna array is derived, using certain available measured data. The distortion in the temporal-angular radiation patterns due to the non-ideal true time delay behavior may be predicted using the presented work. It also facilitates to distinguish between the effects of long and short ripples. This new mathematical investigation is applicable to any linearly chirped fiber Bragg grating other than multi-channel ones. It also includes corrections to previously published formulations.

Limitations by Group Delay Ripple on Optical Beam-forming With Chirped Fiber Grating

This paper investigates the effect of group delay ripple on optical beam-formers using chirped fiber grating. Such optical beam-formers were promised to have many advantages over their electrical beam-forming counter-parts. However, mathematical analysis and simulation results have shown that the group delay ripple causes many drawbacks such as the limitation in operation frequency, RF signal bandwidth, and the number of elements. The most advantageous feature of optical beam-formers, which is squint-free operation for wideband, high frequency signals, is severely affected when chirped grating is used.

Optical Beamforming Networks Based on Broadband Optical Source and Chirped Fiber Grating

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We propose a photonic beamforming network scheme based on a broadband optical source and chirped fiber grating. The principle and feasibility are proved by both theoretical analysis and experiments. In 1- to 18-GHz microwave band, experimental results show a good delay time consistency and the ratio of signal-to-noise met the practical application demands. The time consistency errors are smaller than 1 ps in 9.25- to 10.25-GHz band. Especially, the effects of group delay ripple are effectively mitigated compared with the tunable laser source scheme, which agree well with the theoretical results. </para>

Phase shift of recovered clock due to group delay ripple in fiber Bragg grating and PMD

AbstractThe effect of group delay ripple in fiber bragg grating and polarization mode dispersion on the phase shift of recovered clock signal and the sampling time shift is theoretically and experimentally investigated in 42.8 Gbit/s WDM recirculating transmission, which may result in significant BER degradation in high speed transmission. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3066–3068, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22935

Effect of group delay ripple on picosecond pulse compression schemes

We show experimentally, through autocorrelation and frequency-resolved optical gating measurements, that a simple dispersive fiber Bragg grating with group delay ripple approximately 10 ps peak-to-peak may be used effectively to stretch ultrashort optical pulses for linear amplification before recompression to a higher-power pulse. We further investigate, through simulations, the effect of group delay ripple on the pulses and show that there are regimes, defined by both ripple magnitude and ripple period as a function of wavelength, in which the pulses are nearly perfectly compressed. A map with contours of equal figures of merit indicates favorable regions of operation.

The effect of the group delay ripple of chirped fiber grating on composite second-order in optical fiber CATV system

The effect of group delay ripple of chirped fiber gratings on composite second-order (CSO) performance in optical fiber CATV system is investigated. We analyze the system CSO performances for different ripple amplitudes, periods and residual dispersion amounts in detail. It is found that the large ripple amplitude and small ripple period will deteriorate the system CSO performance seriously. Additionally, the residual dispersion amount has considerable effect on CSO performance in the case of small ripple amplitude and large ripple period.

Impact of Group-Delay Ripple in Transmission Systems Including Phase-Modulated Formats

We derive an analytic expression for the signal distortion that results from the effects of group-delay ripple (GDR). When reduced to its simplified first-order form, our expression provides a clear physical picture of how the signal is affected by the ripple period, magnitude, and how the mean signal frequency is located with respect to the ripple peaks. We also find the optical signal-to-noise ratio penalty associated with the ripple to be dependent on the phase relationship among the signal bits. Particular analysis on the impact of GDR in differential phase-shift keying transmission is presented.

Impact of group delay ripple on repetition-rate multiplication through Talbot self-imaging effect

In repetition-rate multiplication by phase-filtering, chirped fibre Bragg gratings (CFBGs) are often used as the linearly dispersive medium. We analyse the effect of group delay ripple (GDR) in resonant dispersive devices, such as CFBGs, on the rate-multiplied pulse train, and associate it with the unwanted amplitude jitter often observed experimentally. We find that, even at the ideal dispersion required by the so-called Talbot condition, amplitude jitter can be caused by GDR whose frequency components are close to the integer multiples of the reduced bit-period.

Influence of grating group delay ripple on the reduction of dispersion induced intensity noise in subcarrier multiplexed systems

Linearly chirped fiber Bragg gratings (LCFBGs) have been proposed as a means for reducing dispersion induced intensity noise in subcarrier multiplexed systems. We analyze the effects of group delay ripple in LCFBGs on their ability to reduce dispersion induced intensity noise. We find that for typical ripple periods from 5 to 200 pm, even a 20 ps peak-to-peak amplitude ripple, which is near state-of-the-art performance, can degrade the amount of relative intensity noise reduction provided by LCFBGs.