This paper introduces subcarrier pairing to optical OFDM systems and shows, using simulations, that the sensitivity of Direct-Detection Optical Orthogonal Frequency Division Multiplexed (DDO-OFDM) systems can be improved by 0.7 dB, without any coding overheads. Subcarrier pairing works because each subcarrier acquires a different electrical Signal to Interference plus Noise Ratio (SINR), which ...

Photonic sensors have been developed for use in many laboratory and industrial environments for detection of a wide variety of physical, biological and chemical parameters. Both free space and guided wave optical sensors have been demonstrated for use in such diverse applications as food processing, electric power generation, jet engines, oil production, radiation detection, chemical and biolog...

Optical imaging of physiological events in real time can yield insights into biological function that would be difficult to obtain by other experimental means. However, the detection of all-or-none events, such as action potentials or vesicle fusion events, in noisy single-trial data often requires a careful balance of tradeoffs. The analysis of such experiments, as well as the design of optica...

The reliable detection, sizing, and sorting of viruses and nanoparticles is important for biosensing, environmental monitoring, and quality control. Here we introduce an optical detection scheme for the real-time and label-free detection and recognition of single viruses and larger proteins. The method makes use of nanofluidic channels in combination with optical interferometry. Elastically sca...

We report a charge sensitive optical detection technique for label-free study of molecular interactions. Traditional label-free optical detection techniques largely rely on the detection of the mass of a molecule, which are insensitive to small molecules. In contrast, the present technique detects the charge of a molecule, where the signal does not diminish with the size of the molecule, thus c...

The impact of dark 1/f noise on fundamental signal sensitivity in direct low optical signal detection is an understudied issue. In this theoretical manuscript, we study the limitations of an idealized detector with a combination of white noise and 1/f noise, operating in detector dark noise limited mode. In contrast to white noise limited detection schemes, for which there is no fundamental min...

For the purpose of kinematic monitoring system a prototype relatively simple and low cost optical Tilt (or inclination) sensor with sensitivity of 50mV/o and a working range of ±50o is presented in this paper. The sensor consists of a cylindrical shaped transparent container with half filled color liquid and an optical source and detector. The sensor principle based on temporal changes in light...

We present a demonstration of coherent homodyne transmission using 2-PSK at 10Gbit/s, with commercial optical components, which leads to new compact integrated receivers and new transmission formats, thus opening new possibilities for future optical systems. Introduction In most telecommunication fields outside the optical scenario, transmission systems are based on coherent detection, i.e., on...

An Optical FHR Detection System Our research team proposed a low-power optical technique based on the photoplethysmogram (PPG) signal, which is generated when a beam of light is modulated by blood pulsations, to noninvasively estimate the FHR. The doctor or technician shines a beam of LED light (less than 68 mW) at the maternal abdomen, modulated by the blood circulation of the mother and fetus...