The present invention is directed to a self-penetrating percutaneous optical sensing device for obtaining and transmitting optical signal from intravascular fluid in a blood vessel, the device comprising: (a) an elongated hollow rigid sensor sheath 20 having a proximal end 21, a distal end 22 and a central channel extending along the sensor sheath, wherein the distal end 22 of the sensor sheath 20 is sufficiently sharpened to puncture a cutaneous barrier and the sensor sheath 20 has a sufficient length to allow the sensor sheath 20 to penetrate into intravascular space of a blood vessel (b) a flexible optical fiber 30 having a proximal end and a distal end situated coherently within the central channel of the sensor sheath 20 wherein the sensor sheath 20 covers a portion of the distal end of the flexible optical fiber 30 and wherein the distal end of the flexible optical fiber 30 aligns with the distal end 22 of the sensor sheath 20 and (c) an optical sensor 40 connected to the distal end of the flexible optical fiber 30 wherein optical signal generated at the optical sensor 40 can be transmitted from the optical sensor 40 to the proximal end of the flexible optical fiber 30 via the flexible optical fiber 30 and wherein the optical sensor 40 has direct access to the intravascular fluid of the blood vessel.
