Cardiac output can be measured from the rate of absorption of soluble inert gas across the lung using an electric model of human body suggested by W. Mapleson. Step response of the model becomes the sum of exponentials. Cardiac output is estimated from time constants and amplitude coefficients of the response. System for the measurement of the cardiac output which is based on this theory will be introduced below.

Macrobending characteristics of a newly developed hetero-core splicing sensor is investigated from the viewpoint of the practical use intended both for relatively large distortion monitoring and for liquid adhesion detection. The hetero-core sensor can be simply fabricated by fusion splicing of a hetero-core fiber portion as short as approximately 5 mm in length, which is inserted in a typical low-transmission-loss single mode fiber with a 9-µm core diameter for the wavelength of 1.3 µm as a fiber network line. Two types of the sensor are typically realized in terms of the core diameters of 3 and 5 µm for the inserted hetero-core portion which are referred to as 9-3-9 and 9-5-9 types, respectively , with showing their distinct bending loss characteristics. This paper deals with the explorative applications of the two types of hetero-core sensors in which a bending-to-linear displacement converter and a liquid adhesion sensor are successfully examined using a 9-5-9 structure with its low insertion loss and a cladding interactive 9-3-9 structure with its high sensitivity, respectively. The low-insertion loss 9-5-9 sensor has shown the capability of monitoring millimeters-order distortion in low transmission loss fiber networks. On the other hand, the 9-3-9 type has found to be a prospective sensor for liquid adhesion detection. Operational mechanisms for these two sensors are also discussed in terms both of optical leaks occurring at the hetero-core interfaces and of the build-up of cladding modes which might interrogate the outer cladding boundary conditions of the hetero-core sensor.