Abstract: An optical fiber bundle with a assembling tool, which comprises a plurality of optical fibers 3 fusion-bonded and fixed, at one end or both ends thereof, in a hollow part of the assembling tool with substantially no space left therein, wherein at least a portion of said assembling tool 1 in contact with said optical fibers 3 is formed of a thermoplastic resin and provided that Tp represents the heat transformation temperature of said thermoplastic resin and Tc represents the heat transformation temperature of the core material of said optical fibers 3, the following equation (1):Tc-5.ltoreq.Tp.ltoreq.Tc+5 (1)is satisfied. In the optical fiber bundle with a assembling tool according to the present invention, the optical fibers 3 are fixed firmly in the assembling tool 1 and at the same time, are free of the cross-sectional distortion.

Abstract: Disclosed is an instrument for measuring living body components, which has (i) a fine tube having at one end thereof a connection portion to be connected to an indwelling needle or indwelling catheter and an infusion portion, from which at least a blood anticoagulant solution can be infused, (ii) a fine linear sensor for measuring living body components, extended from the inferior of the fine tube to the outside through the connection portion, and (iii) a mechanism for introducing blood at least into the interior of a fine tube portion of the indwelling needle or catheter intermittently or periodically when the indwelling needle or catheter is connected to the fine tube and kept in the blood vessel and then discharging blood into the blood vessel. A sensing portion of the sensor is located within the fine tube portion of the indwelling needle or catheter when the indwelling needle or catheter is connected to the connection portion of the fine tube.