Anna Grazia Mignani

In-vivo biomedical monitoring by fiber-optic systems

An overview of fiber optic sensors for in vivo biomedical monitoring is given, with particular attention to the advantages that these sensors are able to offer compared to the performance of traditional devices. >

BIOMEDICAL SENSORS USING OPTICAL FIBRES

Optical techniques developed for sensing purposes proved to be essential in many application fields, ranging from aerospace, industry, process control, to security, and also medicine. The capabilities of these sensors are generally enhanced when a bulk-optical configuration is replaced by optical fibre technology. In the past few years, research programmes and also the market for fibre sensors have assumed a relevant role. This is undoubtedly due to the growing interest in optoelectronics, but also to the very satisfactory performance and reliability that optical fibre sensors are now able to provide. This paper focuses on the advantages that optical fibre sensors offer to the biomedical field, recalls the basic working principles of sensing, and discusses some examples. This review was received in July 1995

Fibre-optic sensors in health care

Biomedical fibre-optic sensors are attractive for the measurement of physical, chemical and biochemical parameters and for spectral measurements directly performed on the patient. An overview of fibre-optic sensors for in vivo monitoring is given, with particular attention paid to the advantages that these sensors are able to offer in different application fields such as cardiovascular and intensive care, angiology, gastroenterology, ophthalmology, oncology, neurology, dermatology and dentistry.

Distributed fiber brillouin strain sensing with 1cm spatial resolution by correlation-based continuous wave technique

Distributed strain measurement along an optical fiber is performed by a correlated-based continuous wave technique using Brillouin scattering. We demonstrate the spatial resolution of 1cm, which is quite difficult to be achieved by conventional techniques using a pulsed lightwave.

A correlation-based continuous-wave technique for measuring Brillouin gain spectrum distribution along an optical fiber with centimeter-order spatial resolution

A technique to measure Brillouin gain spectrum distribution along an optical fiber with cm spatial resolution is developed. This technique employs frequency-modulated pump and probe lightwaves, which are generated by a direct-frequency-modulation of a laser diode. The frequency difference of about 11GHz between the pump and prove are generated by two ways. The former is a precise way, and the latter is a simple way. The Brilloum gain spectrum is measured at the position of the fiber where the pump-probe correlation is high. The position to be measured is chosen through the frequency of the direct frequency modulation. While the conventional pulse-based technique suffers the spatial resolution limit of several meters imposed by the acoustic damping time, our correlation-based one circumvents it. A spatial-resolution of about 6.5 cm has been demonstrated with this technique. Moreover, a noise compensation technique is also presented.

In vivo biomedical monitoring by fiber optic systems

The development of fiber optic sensors for medical applications originated nearly twenty years ago 1-2 and has been expanding ever since. The success of these sensors is a result of the simplicity of the sensorphysician interface and their notable degree of reliability and biocompatibility. Fiber optic sensors fully satisfy the requisite of biocompatibility, i.e., they do not adversely affect the body nor are they adversely affected by it3 .

Anti-biofouling coatings for optical fiber sensors

One of the most serious problems relevant to the use of optical fiber sensors in real-world environments is surface fouling, that is, the cumulative build-up of undesirable material on the working surface of a sensor. This paper present the results of anti-biofouling tests on coated fiber optic probes for reflectance spectroscopy in blood- simulating foul media, namely Bovine Serum Albumin (BSA) and Fibrinogen. The anti-biofouling coating, a proprietary invention of Biocompatibles Ltd., was a cross-linkable Phosphorylcholine (PC) polymer with Silane functionality, to improve adhesion to silica-containing substrates. All tests in BSA and Fibrinogen showed that PC-1036 coating was efficient in avoiding the build-up of biological material. In fact, optical signal variations of un-coated probes showed fluctuations in the 6-20% range, while coated probes exhibited a nearly-stable optical signal. These results were also confirmed by a microscopic check, which showed adhesions of biological material to un-coated probes.

Model for an Optical Fiber pH Sensor

Sensing pH by fiber optics is based on colorimetric method; indicators which change their own colour with the change of acidity of the solution under study 1 or fluorescent substances, whose fluorescence varies with the pH of solution, 2 can be used to modulate the intensity of the light carried by optical fibers.

Drift induced by faraday effect in twin-depolarizer I-FOG - : Simulatin and experiment

Drift due to Faraday effect in twin-depo-I-FOG is simulated by the general formula, and is also experimented, considering bend-induced-linear-birefringence and intrinsic/extrinsic random birefringence. A way to reduce the drift is also discussed.

Stress-location measurement along an optical fiber by synthesis of rectangular-shaped optical coherence function

A fiber-optic stress-location sensor is proposed by synthesis of rectangular-shaped optical coherence function. By shifting the edge of the coherence function with judgement which side the stress is appeared, its location is determined with spatial-resolution of the full-range/2n by the n times judgement.