Passband flattened binary-tree structured add-drop multiplexers using sion waveguide technology

When writing this introduction I saw the following press release on the Internet: “Nielsen//Netratings reports a record half billion people worldwide now have home internet access‿. The number of home users grew worldwide with 5 % over the last quarter of 2001. The growth was nearly doubled compared to Q3 2001. The growth in Europe was 4.9%, almost equal to the world growth. One in three households in Europe/Middle East and Africa have Internet access, compared with over half in the US. The Netherlands has 52 % of the households connected to the Internet and 82 % of the computers is connected to the Internet. Another press release also fromNielsen//Netratings was titled as “Broadband Usage Outpaces Narrowband for the first time.‿ 1.19 billion of the total 2.3 billion hours was spent by broadband surfers online in January 2002 in the US. The broadband time spent in January 2002 was 64 % higher than in January 2001. Nearly 21.9 million surfers (in the US) at-home accessed the Internet via broadband connection in January 2002 compared to 13.1 million in January 2001, a boost of 67% in one year time. So there is an unstoppable march towards broadband. (See www.nielsen-netratings.com) This demand can be fulfilled with the tremendous bandwidth of the optical fiber of 30 THz (1420-1670 nm). It is not possible to directly address this complete band, since the current maximum speed of the electronics and modulators is 40-100 GHZ. Wavelength division multiplexing (WDM) is used to divide the band in multiple sub bands. The spacing between the sub band channels is defined by the ITU grid. Common spacings between channels are 12.5, 25, 50, 100 and 200 GHz. The device that combines these channels onto one fiber is called a Multiplexer (Mux) and the device that does the opposite, spatial separation of frequency channels onto different fibers, is called a demultiplexer (Demux). When Mux and Demux are combined it is possible to select only one (or more) channel to be dropped or added and leaving the remaining channels undisturbed. Such a device is called an Add-drop multiplexer(ADM). Optical transmission systems 3.28 Tbit/s over a few hundred of kilometers[Nielsen 2000] or 2 Tbit/s over almost ten thousand kilometers [Yamada 2002] have already be reported

On chip frequency discriminator for microwave photonics signal processing

Microwave photonics (MWP) techniques for the generation, distribution and pro- cessing of radio frequency (RF) signals have enjoyed a surge of interest in the last few years. The workhorse behind these MWP functionalities is a high performance MWP link. Such a link needs to fulfill several criteria namely high link gain, low noise figure and high spuriousfree dynamic range (SFDR). High SFDR dictates high linearity and low noise in the links. In a conventional intensity modulated direct detection (IMDD) link the SFDR is mainly limited by the laser relative intensity noise (RIN) and the third order intermodulation distortion (IMD) either from the directly modulated laser or the electro-optic modulator

Enhancement of multioctave dynamic range in a push-pull modulated analog photonic link

We demonstrate an analog photonic link with a high multioctave spurious-free dynamic range (SFDR) using a push-pull modulation technique of laser diodes combined with a balanced detection scheme. SFDR enhancements ranging from 5 dB to 18 dB, relative to the case of a single arm link, have been obtained in a frequency range of 2.5 GHz to 3.2 GHz

A Novel Modulation Scheme for Noise Reduction in Analog Fiber Optic Links

A novel balanced modulation and detection scheme for analog fiber optic links is proposed to overcome the limitations in signal-to-noise ratio (SNR) and dynamic range (DR). In this scheme, the modulating signal is split into positive and negative halves and applied to a pair of laser diodes. Both arms of the link will convey a half-wave rectified version of the signal. At the receiving end the signal is restored via differential detection. Calculation results show that significant improvement in link SNR together with suppression of second-order distortions are achieved

Direct experimental observation of pulse temporal behavior in integrated-optical ring-resonator with negative group velocity

We report a direct experimental observation of pulse temporal behavior in an integrated optical two-port ring-resonator circuit as a function of coupling strength, including the transition across the critical coupling point. We demonstrate the observation of pulse ‘advancement’ in the negative v_g regime and pulse delay in the positive v_g regime. We also observed a smooth transition of the pulse shape from highly negative to highly positive v_g (or vice versa) through a pulse splitting phenomenon. The observed phenomena agree well to theoretical simulations

'Slow'- and 'fast'-light in a single ring-resonator circuit: theory, experimental observations, and sensing applications

Transfer matrix method (TMM) was used to study the phenomena of ‘slow’- and ‘fast’-light in a single two-port ring-resonator (TPRR) circuit theoretically. Their classifications into ‘slow’- and ‘fast’-light with negative and positive group velocity (v_g), where ‘slow’ means |v_g|<c and ‘fast’ means |v_g|>c, will be introduced. The role of such phenomena in controlling light-matter interaction and pulse delay/’advancement’ will be discussed. Direct experimental observations on pulse temporal behaviors in the regimes of ‘slow’- and ‘fast’-light with negative and positive v_g will be demonstrated, showing large and small pulse ‘advancement’ and delay, respectively. Pulse splitting phenomenon as a transition from a highly delayed to a highly ‘advanced’ pulse and vice versa, will also be experimentally demonstrated. Theoretical simulations on the pulse delay and ‘advancement’ based on the TMM and Fourier transform, which show a good qualitative agreement to the experimental results, will also be presented. The exploitation of ‘slow’-light, either with positive or negative v_g for enhancing light-matter interaction will be discussed through evaluating their effects to the performance of integrated-optical refractometric sensor. It will be shown that when the light is ‘slow’, either with negative or positive v_g, there is enhancement of the sensor sensitivity. An integrated-optical sensor which exploits such properties and exhibits sensitivity of one order better than the present day state-of-the-art commercial Mach-Zehnder interferometer refractometric sensor, will be presented

Observing 'back to the future' phenomenon with photonic chip

The possibility to engineer the group velocity $(v_g)$ of light has attracted much attention in the last couple of years. One of the most exotic phenomena in this research field is the negative $v_g$phenomenon. Negative $v_g$ implies that if we send light pulse into the optical medium, the peak of the output will leave the output before the peak of the input pulse entering the medium, i.e. a pulse 'advancement' or negative delay. This paper will discuss such counter-intuitive 'back-to-the-future' phenomenon and its direct time-domain experimental observations on a real photonic chip using measurement equipments available in a typical optical telecommunication laboratory. Comments on the consistency of the phenomenon with the causality principles as well as possible application will also be briefly discussed

Ring resonator-based Tunable Optical Delay Line in LPCVD Waveguide Technology

Optical circuits providing a time delay to signals modulated on optical carriers are considered important for optical communication systems and phased array antennas. A continuously tunable optical delay line is demonstrated in low-cost CMOS compatible LPCVD planar waveguide technology. The device consists of three cascaded ringresonator all-pass filters with fixed circumference of 2 cm (delay of 0.12 ns and FSR of 8.4 GHz). The measured group delay ranges from 0 ns up to 1.2 ns with a bandwidth of 500 MHz and delay ripple smaller than 1 ps, which is in accordance with the calculations