it has been discovered that light can be measured with excellent sensitivity , accuracy and precision in small ( i . e ., nanoliter to microliter ) sample volumes in wells of microplates , or from lab chips ( lab - on - a - chip ) using a compact apparatus that is optimized to read microplates having at least 96 , 384 or 1536 wells per microplate . the sample is illuminated by high intensity light produced by a light source such as , but not limited to , a laser light source , in particular a compact laser diode . the light transmitted via a fiber bundle excites the sample , which converts the excitation light into emission light upon biomolecular binding occurrence . the emitted light is transmitted via a fiber bundle to a detector , such as , but not limited to , a photomultiplier tube , which detects and measures the amount of light after excitation ceases . the fiber bundles that transmit light at the excitation and emission wavelength bands are combined such that the common end of the bundle directly above the well includes both fiber types . the use of high intensity light results in extraordinary assay sensitivity , accuracy and precision . the system utilizes a shutter to shield the detector from this high intensity light during sample excitation . the system can also include a band - pass filter on the emission side , which eliminates extraneous light , including light corresponding to the excitation wavelength band . it has also been discovered that the system of the present invention can be used in assays based on the loci technique . the amount of light produced by the sample is proportional to the concentration of an analyte in the sample and the excitation wavelength is between 670 to 690 nm . the light can be efficiently generated by employing a high - intensity laser as the excitation source , emitting in the preferred wavelength region . the light emitted from the loci sample has a wavelength band between about 520 nm and 620 nm . this range is at a shorter wavelength than that of the excitation wavelength band . the high - intensity light is prohibited from entering the light detector by means of a shutter , which is closed while the light source is active . after the excitation source is turned off , the shutter is opened , and this allows the light indicative of the analyte to enter the detector . it has been further discovered that , in most applications , the light detector can be protected by either a mechanical , electronic or optical shutter , photomultiplier tube - gating device or by interference filters having high out - band blocking properties . the shutter prevents light from entering the detector while the laser diode is active , the filter prevents light outside the emitted wavelength band from entering the detector . the preferred detector is a standard photomultiplier tube . a laser diode must emit sufficient light to produce the required assay performance . generally , the maximum power output of the laser diode should be from approximately 1 milliwatt ( mw ) to 1 watt , preferably from 30 mw to 200 mw . the light is carried to and from the well by fiber bundles . any fiber bundle that transmits light at the wavelength of interest can be used in connection with this invention . however , the preferred fiber bundles are bundles consisting of fused silica multimode fibers , having diameters between 50 and 500 micrometers . the filter used to eliminate extraneous light , including that which corresponds to the excitation wavelength band , can be any narrow or broad , optical filter capable of transmitting light in the emission wavelength band of interest and blocking light in the out - band emission wavelength region . the preferred filters are interference filters or colored - glass filters . the light bundles are combined at the end facing the well in a configuration that allows the emitted light to be collected efficiently , and transmitted to the detector . preferably , the fibers transmitting the excitation light are in the center of the end section , and occupy a low percentage of the overall bundle diameter . generally , the ratio of the cross - sectional area of fibers transmitting light from the excitation light source , to the cross - sectional area of fibers transmitting light to the detector , is in the approximate range from 0 . 01 to 50 percent , preferably from 1 to 10 %. the preferred embodiment of the present invention is shown in the accompanying drawings . fig1 and 2 display an analyzer , designated by the numeral 10 , which is constructed in accordance with the present invention . the analyzer 10 includes a laser diode 12 and a lens compartment 14 containing two lenses . the currently preferred laser diode is cql806 / 30 diode marketed by philips . this diode emits light at 675 nm at a maximum optical output power of 30 mw . the cql802 / d diode marketed by philips produces three times higher signal levels ; however , the cost of this device is also three times higher compared to other commonly used diodes . thus , it is preferred only for applications where the cql806 / 30 diode does not provide sufficient optical illumination power for the desired assay performance . the two lenses are not shown in fig1 but are shown in fig2 and are designated by numerals 16 and 17 . as shown schematically in fig2 light 18 emitted by the laser diode 12 , is directed by the lenses 16 and 17 into a fiber bundle 20 . currently , preferred fiber bundles consist of individual multimode fibers made of fused silica with a numerical aperture of 0 . 22 to 0 . 4 . the total diameter of the currently preferred bundle is approximately 3 mm at the sample end . coaxial fiber arrangement at the common end is preferred , especially for 1536 - well plates , because the light at the excitation wavelength could be dispersed over adjacent wells in the microplate . as shown in fig1 and 2 , the fiber bundle 20 extends from the lens compartment 14 to a well of a microplate 22 . currently preferred are microplates having either 96 , 384 or 1536 wells . the fiber bundle 20 is joined with the fiber bundle 24 to form a bifurcated bundle 26 . to improve light collection efficiency and reduce cross - talk between wells in a microplate , a lens ( not shown ) is mounted at the sample end of the bifurcated bundle 26 . the lens collimates the light emerging from the excitation fibers and directs it into the sample well . the lens defines the field of view in the well by its clear aperture and its numerical aperture . this is needed to mask the effective area from which the emitted light is collected to a size suitable for wells with different diameters . a lens having about a 3 mm diameter is preferred for 1536 - well microplates , while larger clear - aperture lenses are preferred for lower density microplates , such as 384 - well microplates . the use of high - numerical aperture lenses is preferred since more light emerging from the sample well can be collected . a typical numerical aperture shall be 0 . 5 . the lens should be placed between 0 . 25 mm and 2 mm above the microplates . the preferred distance is 1 mm . the construction of the fiber bundles 20 , 24 and 26 is shown in fig3 and 4 . as displayed in fig3 fiber bundles 20 and 24 are joined by a transition piece 30 . as shown in fig4 the bifurcated fiber bundle 26 has 169 fibers . seven of these fibers , which are darkened and designated by a numeral 32 , are the excitation fibers . one hundred sixty - two of the fibers located around the excitation fibers are the emission fibers , denoted by 33 . the light carried by the fiber bundle 20 enters into the fiber bundles 32 . the light then enters the medium of the well and the emitted light is collected by the fibers 33 . the emitted light is carried by fibers 33 into the fiber bundle 24 . as shown in fig1 and 2 , the fiber bundle 24 transmits emitted light to the emission assembly 35 . as shown schematically in fig2 the emission assembly 35 includes a lens 37 , which collimates the light collected from the fiber bundle 24 and directs it into an emission band - pass filter 36 . since the laser diode emits a large amount of light at 680 nm , the emission filters must effectively block this light to prevent damage to the photomultiplier tube if no shutter is used . at the present time , the custom 570df100 filter manufactured by omega optical , inc ., is preferred . the emission band - pass filter 36 transmits light in the 520 - 620 nm wavelength range through a mechanical shutter 39 into a photomultiplier module 41 . the currently preferred photomultiplier module is h6240 - 01 , including a photomultiplier tube that has increased sensitivity in the emission wavelength of interest . this module is marketed by hamamatsu photonics . the hardware and user interfaces are controlled by an in - house developed software package , which includes full instrument control , assay definition , sample mapping , data storage and reporting , and database management . another embodiment of the fiber bundle for use in the analyzer of the present invention is shown in fig5 . the fiber bundle 50 shown in fig5 collects light emitted from a single laser diode ( not shown ) and directs the light to four fiber bundles 52 , 54 , 56 and 58 . the fiber bundles 52 , 54 , 56 and 58 which are joined with corresponding emission fiber bundles 62 , 64 , 66 and 68 in the same manner as the fiber bundles shown in fig3 to produce the cross - sectional view as shown in fig4 . fig5 shows an example of having one common light source for measuring four samples in four different wells simultaneously by means of four emission assemblies . other numbers of light sources and detectors per channel are possible . in particular , the combination of having one light source illuminating multiple wells , and one ( multi - channel ) detector to detect the emission light of multiple wells can be implemented . the following examples are provided to further illustrate the present invention . they are not intended to limit the present invention in any manner . in this example , an antiphosphotyrosine antibody is conjugated to the loci chemiluminescer bead . streptavidin is conjugated to the loci sensitizer bead . biotinylated phosphotyrosine peptide is diluted in assay buffer to known concentrations . appropriate volumes of each component are added to wells of a microplate , mixed , and incubated . the microplate is then loaded into the measurement apparatus and the light emitted by each well is measured . the light intensity is proportional to the concentration of the biotinylated phosphotyrosine peptide . fig6 depicts typical results for a range of sample volumes . other experiments have demonstrated a sensitivity of 125 femtograms of the phosphotyrosine peptide in as little as 60 nl in a labchip , wherein reagents are dispensed , mixed , incubated , and analyzed in an integrated miniaturized disposable device . in this example , an anti - gst antibody is conjugated to the loci chemiluminescer bead . streptavidin is conjugated to the loci sensitizer bead . biotinylated gbγ protein is diluted in assay buffer to a known concentration . appropriate volumes of each component are added to wells of a microplate , mixed , and incubated . the microplate is then loaded into the measurement apparatus and the light emitted by each well is measured . the light intensity is proportional to the concentration of the biotinylated gbγ protein . fig7 depicts typical signal to blank ratios for a range of sample volumes and microplate formats . in this example , an anti - tnfαri antibody is conjugated to the loci chemiluminescer bead . streptavidin is conjugated to the loci sensitizer bead . biotinylated tnfα and tnfαri receptor are diluted in assay buffer to known concentrations . appropriate volumes of each component are added to wells of a microplate , mixed , and incubated . the microplate is then loaded into the measurement apparatus and the light emitted by each well is measured . the light intensity is proportional to the concentration of the biotinylated tnfαri fig8 depicts typical signal to blank ratios for a range of sample volumes and microplate formats .