Abstract:
A pitch side optical system for use in diode laser spectroscopy consisting of more than one diode laser having select lasing frequencies with each diode laser being coupled to an end of a distinct input optical fiber. The pitch side optical system further consists of a multiplexer optically coupled to the other end of less than all of the input optical fibers with the multiplexer outputting multiplexed laser light to a pitch side optical fiber. The pitch side optical system further consists of a coupler optically coupled to the far end of the pitch side optical fiber and the far end of an unmultiplexed input optical fiber with the coupler combining the multiplexed laser light and the unmultiplexed laser light and outputting the combined light to a transmission optical fiber. Typically, the coupler is located near the combustion process. The pitch side optical system further consists of a pitch optic coupled to the transmission optical fiber. Typically, all optical fibers used in the pitch side optical system are single mode optical fibers.
Abstract:
A sensing apparatus consisting of more than one diode laser having select lasing frequencies, a multiplexer optically coupled to the outputs of the diode lasers with the multiplexer being further optically coupled to a pitch side optical fiber. Multiplexed laser light is transmitted through the pitch side optical fiber to a pitch optic operatively associated with a process chamber which may be a combustion chamber or the boiler of a coal or gas fired power plant. The pitch optic is oriented to project multiplexed laser output through the process chamber. Also operatively oriented with the process chamber is a catch optic in optical communication with the pitch optic to receive the multiplexed laser output projected through the process chamber. The catch optic is optically coupled to an optical fiber which transmits the multiplexed laser output to a demultiplexer. The demultiplexer demultiplexes the laser light and optically couples the select lasing frequencies of light to a detector with the detector being sensitive to one of the select lasing frequencies.
Abstract:
This invention is generally concerned with sensing apparatus and methods, more particularly apparatus and methods for sensing techniques based upon cavity ring-down spectroscopy (CRDS). An evanescent wave cavity-based optical sensor is described. The sensor comprises an optical cavity formed by a pair of highly reflective surfaces (108, 110) such that light within said cavity makes a plurality of passes between said surfaces, an optical path between said surfaces including a reflection from a totally internally reflecting (112) surface, said reflection from said reflection from said surface generating an evanescent wave to providing a sensing function; a light source (102) to inject light into said cavity; and a detector (114) to detect a light level within said cavity; whereby absorption of said evanescent wave is detectable using said detector to provide said sensing function; wherein said light source comprises a continuous wave light source; and wherein said light source has a power and bandwidth sufficient to couple energy into at least two modes of oscillation of said cavity to overcome losses within the cavity and excite at least two modes of oscillation of said cavity.