Patent Description:
Conventional smoke detection systems operate by detecting the presence of smoke or other airborne pollutants. Upon detection of a threshold level of particles, an alarm or other signal, such as a notification signal, may be activated and operation of a fire suppression system may be initiated.

High sensitivity smoke detection systems may incorporate a pipe network consisting of one or more pipes with holes or inlets installed at positions where smoke or prefire emissions may be collected from a region or environment being monitored. Air is drawn into the pipe network through the inlets, such as via a fan, and is subsequently directed to a detector. In some conventional smoke detection systems, individual sensor units may be positioned at each sensing location, and each sensor unit has its own processing and sensing components.

Delays in the detecting the presence of the fire may occur in conventional point smoke detectors and also pipe network detection systems, for example due to the smoke transport time. In pipe network detection systems, due to the size of the pipe network, there is a typically a time delay between when the smoke enters the pipe network through an inlet and when that smoke actually reaches the remote detector. In addition, because smoke or other pollutants initially enter the pipe network through a few of the inlets, the smoke mixes with the clean air provided to the pipe from the remainder of the inlets. As a result of this dilution, the smoke detectable from the smoke and air mixture may not exceed the threshold necessary to indicate the existence of a fire.

<CIT> discloses an optical smoke detection module for a fire alarm system.

The present invention provides a detection system for measuring one or more conditions within a predetermined area as claimed in claim <NUM>.

Optionally, in further embodiments the modulated light includes pulses of light.

Optionally, in further embodiments the modulated light includes a continuous signal.

Optionally, in further embodiments the predetermined area is one of a building and an avionics bay of an aircraft.

The present invention also provides a method of measuring a condition within a predetermined area as claimed in claim <NUM>.

Optionally, the predetermined area is one of a building and an avionics bay of an aircraft.

The subject matter, which is regarded as the present disclosure, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification.

The detailed description explains embodiments of the present disclosure, together with advantages and features, by way of example with reference to the drawings.

Referring now to the FIGS. , a system <NUM> for detecting one or more conditions or events within a designated area is illustrated. The detection system <NUM> is configured to detect one or more hazardous conditions, including smoke caused by a fire and presence of a person. In addition the detection system <NUM> may be able to detect the presence of fire, temperature, flame, or any of a plurality of pollutants, combustion products, or chemicals. In addition, the detection system <NUM> may be configured to perform monitoring operations of people, lighting conditions, or objects. In claim <NUM> the one or more conditions include smoke caused by a fire and presence of a person. In an embodiment, the system <NUM> may operate in a manner similar to a motion sensor, such as to detect the presence of a person, occupants, or unauthorized access to the designated area for example. Further suitable conditions or events are within the scope of the disclosure.

The detection system <NUM> uses light to evaluate a volume for the presence of a condition. In this specification, the term "light" means coherent or incoherent radiation at any frequency or a combination of frequencies in the electromagnetic spectrum. In an example, the photoelectric system uses light scattering to determine the presence of particles in the ambient atmosphere to indicate the existence of a predetermined condition or event. In this specification, the term "scattered light" may include any change to the amplitude/intensity or direction of the incident light, including reflection, refraction, diffraction, absorption, and scattering in any/all directions. In this example, light is emitted into the designated area; when the light encounters an object (a person, smoke particle, or gas molecule for example), the light can be scattered and/or absorbed due to a difference in the refractive index of the object compared to the surrounding medium (air). Depending on the object, the light can be scattered in all different directions. Observing any changes in the incident light, by detecting light scattered by an object for example, can provide information about the designated area including determining the presence of a predetermined condition or event.

In its most basic form, as shown in <FIG>, the detection system <NUM> includes a single fiber optic cable <NUM> with at least one fiber optic core. The term fiber optic cable <NUM> includes any form of optical fiber. As examples, an optical fiber is a length of cable that is composed of one or more optical fiber cores of single-mode, multimode, polarization maintaining, photonic crystal fiber or hollow core. A node <NUM> is located at the termination point of a fiber optic cable <NUM> and is inherently included in the definition of a fiber optic cable <NUM>. The node <NUM> is positioned in communication with the ambient atmosphere. A light source <NUM>, such as a laser diode for example, and a light sensitive device <NUM>, such as a photodiode for example, are coupled to the fiber optic cable <NUM>. A control system <NUM> of the detection system <NUM>, discussed in further detail below, is utilized to manage the detection system operation and may include control of components, data acquisition, data processing and data analysis.

As shown in <FIG>, the light from the light source is transmitted through the node <NUM> to the surrounding area, illustrated schematically at <NUM>. The light <NUM> interacts with one or more particles indicative of a condition, illustrated schematically at <NUM>, and is reflected or transmitted back to the node <NUM>, illustrated schematically at <NUM>. A comparison of the light provided to the node <NUM> and/or changes to the light reflected back to the light sensitive device <NUM> from the node <NUM> will indicate whether or not changes in the atmosphere are present in the ambient atmosphere adjacent the node <NUM> that are causing the scattering of the light. The scattered light as described herein is intended to additionally include reflected, transmitted, and absorbed light. Although the detection system <NUM> is described as using light scattering to determine a condition or event, embodiments where light obscuration, absorption, and fluorescence is used in addition to light scattering are also within the scope of the disclosure.

In another embodiment, the detection system <NUM> can include a plurality of nodes <NUM>. For example, as illustrated in <FIG>, a plurality of fiber optic cables <NUM> and corresponding nodes <NUM> are each associated with a distinct light sensitive device <NUM>. In embodiments where an individual light sensitive device <NUM> is associated with each node <NUM>, as shown in <FIG>, the signal output from each node <NUM> can be monitored. Upon detection of a predetermined event or condition, it will be possible to localize the position of the event because the position of each node <NUM> within the system <NUM> is known. Alternately, as shown in <FIG>, a plurality of fiber optic cables <NUM>, may be coupled to a single light sensitive device.

In embodiments where a single light sensitive device <NUM> is configured to receive scattered light from a plurality of nodes <NUM>, the control system <NUM> is able to localize the scattered light, i.e. identify the scattered light received from each of the plurality of nodes <NUM>. In an embodiment, the control system <NUM> uses the position of each node <NUM>, specifically the length of the fiber optic cables <NUM> associated with each node <NUM> and the corresponding time of flight (i.e. the time elapsed between when the light was emitted by the light source <NUM> and when the light was received by the light sensitive device <NUM>), to associate different parts of the light signal with each of the respective nodes <NUM> that are connected to that light sensitive device <NUM>. Alternatively, or in addition, the time of flight may include the time elapsed between when the light is emitted from the node and when the scattered light is received back at the node. In such embodiments, the time of flight provides information regarding the distance of the object relative to the node.

In an embodiment, illustrated in the cross-section of the fiber optic cable shown in <FIG>, two substantially identical and parallel light transmission fiber cores <NUM>, <NUM> are included in the fiber optic cable <NUM> and terminate at the node <NUM>. However, it should be understood that embodiments where the fiber optic cable <NUM> includes only a single fiber core, or more than two cores are also contemplated herein. The light source <NUM> may be coupled to the first fiber core <NUM> and the light sensitive device <NUM> may be coupled to the second fiber core <NUM>, for example near a first end of the fiber optic cable <NUM>. The light source <NUM> is selectively operable to emit light, which travels down the first fiber core <NUM> of the fiber optic cable <NUM> to the node <NUM>. At the node <NUM>, the emitted light is expelled into the adjacent atmosphere. The light is scattered and transmitted back into the node <NUM> and down the fiber cable <NUM> to the light sensitive device <NUM> via the second fiber core <NUM>.

With reference now to <FIG>, in more complex embodiments, the detection system <NUM> includes a fiber harness <NUM> having a plurality of fiber optic cables <NUM> bundled together. It should be noted that a fiber harness <NUM> can also be only a single fiber optic cable <NUM>. In an embodiment, a plurality of fiber cores <NUM>, <NUM> are bundled together at a location to form a fiber harness backbone <NUM> with the ends of the fiber optic cables <NUM> being separated (not included in the bundled backbone) to define a plurality of fiber optic branches <NUM> of the fiber harness <NUM>. As shown, the plurality of fiber cores <NUM>, <NUM> branch off to form a plurality of individual fiber branches <NUM>, each of which terminates at a node <NUM>. In the non-limiting embodiments of <FIG>, the fiber harness <NUM> additionally includes an emitter leg <NUM> and a receiver leg <NUM> associated with the fiber branches <NUM>. The emitter leg <NUM> may contain the first fiber cores <NUM> from each of the plurality of fiber branches <NUM> and the receiver leg <NUM> may contain all of the second fiber cores <NUM> from each of the fiber branches <NUM>. The length of the fiber optic cores <NUM>, <NUM> extending between the emitter leg <NUM> or the receiver leg <NUM> and the node <NUM> may vary in length such that the branches <NUM> and corresponding nodes <NUM> are arranged at various positions along the length of the fiber harness backbone <NUM>. In an embodiment, the positions of the nodes <NUM> may be set during manufacture, or at the time of installation of the system <NUM>.

Alternatively, the fiber harness <NUM> may include a fiber optic cable (not shown) having a plurality of branches <NUM> integrally formed therewith and extending therefrom. The branches <NUM> may include only a single fiber optic core. The configuration, specifically the spacing of the nodes <NUM> within a fiber harness <NUM> may be substantially equidistant, or may vary over the length of the harness <NUM>. In an embodiment, the positioning of each node <NUM> may correlate to a specific location within the designated area.

With reference now to <FIG>, the detection system <NUM> may additionally include a plurality of fiber harnesses <NUM>. In the illustrated, non-limiting embodiment, a distinct light sensitive device <NUM> is associated with each of the plurality of fiber harnesses <NUM>. However, embodiments where a single light sensitive device <NUM> is coupled to the plurality of fiber harnesses <NUM> are also contemplated here. In addition, a single light source <NUM> may be operably coupled to the plurality of light transmission fiber cores <NUM> within the plurality of fiber harnesses <NUM> of the system <NUM>. Alternatively, the detection system <NUM> may include a plurality of light sources <NUM>, each of which is coupled to one or more of the plurality of fiber harnesses <NUM>.

The detection system <NUM> may be configured to monitor a predetermined area such as a building. The detection system <NUM> may be especially utilized for predetermined areas having a crowded environment, such as a server room, as shown in <FIG> for example. Each fiber harness <NUM> may be aligned with one or more rows of equipment <NUM>, and each node <NUM> therein may be located directly adj acent to one of the towers <NUM> within the rows <NUM>. In addition, nodes may be arranged so as to monitor specific enclosures, electronic devices, or machinery. Positioning of the nodes <NUM> in such a manner allows for earlier detection of a condition as well as localization, which may limit the exposure of the other equipment in the room to the same condition. In another application, the detection system <NUM> may be integrated into an aircraft, such as for monitoring a cargo bay, avionics rack, lavatory, or another confined region of the aircraft that may be susceptible to fires or other events.

The control system <NUM> of the detection system <NUM> is utilized to manage the detection system operation and may include control of components, data acquisition, data processing and data analysis. The control system <NUM>, illustrated in <FIG>, includes at least one light sensitive device <NUM>, at least one light source, <NUM>, and a control unit <NUM>, such as a computer having one or more processors <NUM> and memory <NUM> for implementing an algorithm <NUM> as executable instructions that are executed by the processor <NUM>. The instructions may be stored or organized in any manner at any level of abstraction. The processor <NUM> may be any type of processor, including a central processing unit ("CPU"), a general purpose processor, a digital signal processor, a microcontroller, an application specific integrated circuit ("ASIC"), a field programmable gate array ("FPGA"), or the like. Also, in some embodiments, memory <NUM> may include random access memory ("RAM"), read only memory ("ROM"), or other electronic, optical, magnetic, or any other computer readable medium for storing and supporting processing in the memory <NUM>. In addition to being operably coupled to the at least one light source <NUM> and the at least one light sensitive device <NUM>, the control unit <NUM> may be associated with one or more input/output devices <NUM>. In an embodiment, the input/output devices <NUM> may include an alarm or other signal, or a fire suppression system which are activated upon detection of a predefined event or condition. It should be understood herein that the term alarm, as used herein, may indicate any of the possible outcomes of a detection.

The processor <NUM> may be coupled to the at least one light source <NUM> and the at least one light sensitive device <NUM> via connectors. The light sensitive device <NUM> is configured to convert the scattered light received from a node <NUM> into a corresponding signal receivable by the processor <NUM>. In an embodiment, the signal generated by the light sensing device <NUM> is an electronic signal. The signal output from the light sensing device <NUM> is then provided to the control unit <NUM> for processing using an algorithm to determine whether a predefined condition is present.

The signal received by or outputted from the light sensitive device(s) <NUM> may be amplified and/or filtered, such as by a comparator (not shown), to reduce or eliminate irrelevant information within the signal prior to being communicated to the control unit <NUM> located remotely from the node <NUM>. In such embodiments, the amplification and filtering of the signal may occur directly within the light sensing device <NUM>, or alternatively, may occur via one or more components disposed between the light sensing device <NUM> and the control unit <NUM>. The control unit <NUM> may control the data acquisition of the light sensitive device <NUM>, such as by adjusting the gain of the amplifier, the bandwidth of filters, sampling rates, the amount of timing and data buffering for example.

With reference now to <FIG>, in an embodiment of the system <NUM>, the light sensitive device <NUM> may include one or more Avalanche Photodiode (APD) sensors <NUM>. For example, an array <NUM> of APD sensors <NUM> may be associated with the one or more fiber harnesses <NUM>. In an embodiment, the number of APD sensors <NUM> within the sensor array <NUM> is equal to or greater than the total number of fiber harnesses <NUM> operably coupled thereto. However, embodiments where the total number of APD sensors <NUM> within the sensor array <NUM> is less than the total number of fiber harnesses <NUM> are also contemplated herein.

Data representative of the output from each APD sensor <NUM> in the APD array <NUM> is periodically taken by a switch <NUM>, or alternatively, is collected simultaneously. The data acquisition <NUM> collects the electronic signals from the APD and associates the collected signals with metadata. The metadata as an example can be time, frequency, location or node. In an example, the electronic signals are from the APD are synchronized to the laser modulation such that the electrical signals are collected for a period of time that starts when the laser is pulsed to several microseconds after the laser pulse. The data will be collected and processed by the processor <NUM> to determine whether any of the nodes <NUM> indicates the existence of a predefined condition or event. In an embodiment, only a portion of the data outputted by the sensor array <NUM>, for example the data from a first APD sensor <NUM> associated with a first fiber harness <NUM>, is collected. The switch <NUM> is therefore configured to collect information from the various APD sensors <NUM> of the sensor array <NUM> sequentially. While the data collected from a first APD sensor <NUM> is being processed to determine if an event or condition has occurred, the data from a second APD <NUM> of the sensor array <NUM> is collected and provided to the processor <NUM> for analysis. When a predefined condition or event has been detected from the data collected from one of the APD sensors <NUM>, the switch <NUM> may be configured to provide additional information from the same APD sensor <NUM> to the processor <NUM> to track the condition or event.

A method of operation <NUM> of the detection system <NUM> is illustrated in <FIG>. The control unit <NUM> operably coupled to the light source <NUM> is configured to selectively energize the light source <NUM>, as shown in block <NUM>, and to emit light to a fiber harness <NUM> coupled thereto as shown in block <NUM>. Based on the desired operation of the detection system <NUM>, the control unit <NUM> varies the intensity, duration, repetition, frequency, or other properties, of the light emitted. As the light travels down the first fiber core <NUM> of the at least one fiber optic branch <NUM>, all or a portion of the light is emitted at one or more nodes <NUM> of the fiber harness <NUM>. In block <NUM>, light is scattered in the predetermined area and transmitted back through the fiber optic branches <NUM> via the second fiber cores <NUM>. The scattered light may include one or more of scattered light within the atmosphere adjacent the node and scattered light that reflects from an interior of the fiber optic branch <NUM>. The scattered light is transmitted to the at least one light sensing device <NUM> in block <NUM>. As shown in block <NUM>, the light sensing device <NUM> generates a signal in response to the scattered light received by each node <NUM>, and provides that signal to the control unit <NUM> for further processing.

Using the algorithm <NUM> executed by the processor <NUM>, each of the signals representing the scattered light received by the corresponding nodes <NUM> are evaluated to determine whether the light at the node <NUM> is indicative of a predefined condition, such as smoke for example. With reference to <FIG>, a schematic diagram illustrating an example of a flow path for processing the signals generated by each of the nodes <NUM> is illustrated. As shown, the signal indicative of scattered light <NUM> is parsed, shown at block <NUM>, into a plurality of signals based on their respective originating node <NUM>. In the illustrated, non-limiting embodiment, background signals, illustrated schematically at <NUM>, are subtracted from the data before the pulse features are evaluated for each of the individual signals. Through integration, pulse compression, and/or feature extraction, shown at block <NUM>, one or more characteristics or features (pulse features) of the signal may be determined. Examples of such features include, but are not limited to, a peak height, an area under a curve defined by the signal, statistical characteristics such as mean, variance, and/or higher-order moments, correlations in time, frequency, space, and/or combinations thereof, and empirical features as determined by deep learning, dictionary learning, and/or adaptive learning and the like.

In an embodiment, the time of flight record is parsed and features are extracted. The time of flight record can cover a period of time. For example, a time of flight record can record light intensity over <NUM> -<NUM>,<NUM>,<NUM> nanoseconds, <NUM>-<NUM>,<NUM> nanosceconds, or <NUM>-<NUM>,<NUM> microseconds. The features extracted from the signal can include, but are not limited to height, full width at half maximum, signal pick up time, signal drop off time, group velocity, integration, rate of change, mean, and variance for example.

Through application of the data processing, illustrated schematically at block <NUM>, the features may then be further processed by using, for example, smoothing, Fourier transforms or cross correlation. In an embodiment, the processed data is then sent to the detection algorithm at block <NUM> to determine whether or not the signal indicates the presence and/or magnitude of a condition or event at a corresponding node <NUM>. This evaluation may be a simple binary comparison that does not identify the magnitude of deviation between the characteristic and a threshold. The evaluation may also be a comparison of a numerical function of the characteristic or characteristics to a threshold. The threshold may be determined a priori or may be determined from the signal. The determination of the threshold from the signal may be called background learning. Background learning may be accomplished by adaptive filtering, model-based parameter estimation, statistical modeling, and the like. In some embodiments, if one of the identified features does not exceed a threshold, the remainder of the detection algorithm is not applied in order to reduce the total amount processing done during the detection algorithm. In the event that the detection algorithm indicated the presence of the condition at one or more nodes <NUM>, an alarm or other fire suppression system may, but need not be activated. It should be understood that the process for evaluating the data illustrated and described herein is intended as an example only and that other processes including some or all of the steps indicated in the FIG. are also contemplated herein.

The evaluation may also advantageously employ classifiers including those that may be learned from the signal via deep learning techniques including, but not limited to deep neural networks, convolutional neural networks, recursive neural networks, dictionary learning, bag of visual/depth word techniques, Support Vector Machine (SVM), Decision Trees, Decision Forests, Fuzzy Logic, and the like. The classifiers may also be constructed using Markov Model techniques, Hidden Markov Models (HMM), Markov Decision Processes (MDP), Partially Observable MDPs, Markov Decision Logic, Probabilistic Programming, and the like.

In addition to evaluating the signals generated from each node <NUM> individually, the processor <NUM> may additionally be configured to evaluate the plurality of signals or characteristics thereof collectively, such as through a data fusion operation to produce fused signals or fused characteristics. The data fusion operation may provide information related to time and spatial evolution of an event or predetermined condition. As a result, a data fusion operation may be useful in detecting a lower level event, insufficient to initiate an alarm at any of the nodes <NUM> individually. For example, in the event of a slow burning fire, the light signal generated by a small amount of smoke near each of the nodes <NUM> individually may not be sufficient to initiate an alarm. However, when the signals from the plurality of nodes <NUM> are reviewed in aggregate, the increase in light returned to the light sensitive device <NUM> from multiple nodes <NUM> may indicate the occurrence of an event or the presence of an object not otherwise detected. In an embodiment, the fusion is performed by Bayesian Estimation. Alternatively, linear or non-linear joint estimation techniques may be employed such as maximum likelihood (ML), maximum a priori (MAP), non-linear least squares (NNLS), clustering techniques, support vector machines, decision trees and forests, and the like.

As illustrated and described above, the processor <NUM> is configured to analyze the signals generated by at least one light sensing device <NUM> relative to time. In another embodiment, the detection algorithm may be configured to apply one or more of a Fourier transform, Wavelet transform, space-time transform, Choi-Williams distribution, Wigner-Ville distribution and the like, to the signals to convert the signals from a temporal domain to a frequency domain. This transformation may be applied to the signals when the nodes <NUM> are being analyzed individually, when the nodes <NUM> are being analyzed collectively during a data fusion, or both.

The relationship between the light scattering and the magnitude or presence of a condition is inferred by measuring a signal's causality and dependency. As an example, the measure of a causality utilizes one or more signal features as an input and determines one or more outputs from a calculation of a hypothesis testing method, foreground ratio, second derivative, mean or Granger Causality Test. Similarly, one or more signal features may be used as an input to evaluate the dependency of a signal. One or more outputs are selected from a calculation of a correlation, fast Fourier transform coefficients, a second derivative, or a window. The magnitude and presence of the condition is then based on the causality and dependency. The magnitude and presence of a condition may be calculated utilizing one or more evaluation approaches: a threshold, velocity, rate of change or a classifier. The detection algorithm may include utilizing the output from the calculation causality, dependency or both. This is used to indicate the presence of the condition at one or more nodes <NUM> and initiate a response.

Because the frequency of smoke varies within a small range, such as from about <NUM> to about <NUM> for example, evaluation of the signals with respect to frequency may effectively and accurately determine the presence of smoke within the predetermined space <NUM>. The detection algorithm may be configured to evaluate the signals in a fixed time window to determine the magnitude of the frequency or the strength of the motion of the smoke. Accordingly, if the magnitude of a frequency component exceeds a predetermined threshold, the detection algorithm may initiate an alarm indicating the presence of a fire. In an embodiment, the predetermined threshold is about <NUM> such that when the magnitude of the optical smoke frequency exceeds the threshold, smoke is present.

In an embodiment, the algorithm <NUM> is configured to distinguish between different events or conditions based on the rate of change in the light scattered by the atmosphere near the node <NUM> and received by one or more of the nodes <NUM> over time. With reference to <FIG>, graphs of the signals recorded from a node <NUM> over time with respect to different events are illustrated. <FIG> indicates the change in the light signal received by a node <NUM> as a person walks through the area being monitored by the node <NUM>. As shown in the graph, the movement of a person appears as steps having varying magnitudes. <FIG>, which represents the detection of smoke from a smoldering fire, appears graphically as a much continuously changing signal having an accelerating increase in the change in light signal received by a node <NUM> over time. It should be understood that the graphs illustrated are examples only. Further, each predefined event detectable by the detection system <NUM> may have one or more unique parameters associated therewith.

According to the invention, to reduce the noise associated with each signal, the light emitting device <NUM> is modulated such that the device <NUM> is selectively operated to generate modulated light in a specific pattern. The light within the pattern varies in intensity, width, frequency, phase, and may comprise discrete pulses or may be continuous. The specific pattern of light is designed to have desirable properties including cross-correlation with a second specific pattern. When the light is emitted in a specific pattern, the light scattered back to a corresponding light sensing device <NUM> should arrive in the substantially same pattern. Use of more than one specific and known pattern provides enhanced processing capabilities by allowing for the system <NUM> to reduce overall noise. This reduction in noise when combined with the signal processing may result in an improved signal to noise ratio and the total number of false events or conditions detected will decrease. Alternatively, or in addition, the device sensitivity may be improved thereby increasing the limits of the detection system <NUM>. By cross-correlating one or more second patterns, specific causes of transmitted or reflected signals are distinguished, e.g. by Bayesian estimation of the respective cross-correlations of the received signal with the one or more second patterns.

In addition, modulation of the light signal emitted by the light source <NUM> may provide improved detection by determining more information about the event or condition causing the scatter in the light signal received by the node <NUM>. For example, such modulation may allow the system <NUM> to more easily distinguish between a person walking through the designated area adjacent a node, as shown in <FIG>, and a smoldering fire adjacent the node <NUM>.

Referring now to <FIG>, in some embodiments the system <NUM> includes one or more optical enhancement devices <NUM>, such as a bandpass filter, a polarizer, an antireflective coating, a wave plate, and/or other optical features to reduce interference from non-event signals, or other non-desired signals, such as ambient light from either sunlight or lighting in the space, or from solid objects in the predetermined space <NUM>. Further, the optical enhancement devices <NUM> may be utilized to reduce undesired wavelengths and/or intensities transmitted from the light source <NUM>. The optical enhancement <NUM> is placed in the system <NUM> downstream of the light source <NUM>, in some embodiments a laser diode, and upstream of the light sensitive device <NUM>, in some embodiments the photodiode. The optical enhancement device <NUM> is placed so that light scattered and reflected back to the light sensitive device <NUM> is passed through the optical enhancement device <NUM> to filter or differentiate events or other conditions to be sensed from other signals due to, for example, ambient light, solid objects, bugs, dust, or water vapor.

As shown in <FIG>, in some embodiments the optical enhancement <NUM> is located at the light sensitive device <NUM> and/or is a component of, integral to or embedded within the light sensitive device <NUM>. Further, the light sensitive device <NUM> may be configured such that the optical enhancement device <NUM> is readily removable and/or replaceable with another optical enhancement <NUM> to filter or disseminate different conditions in the scattered/reflected signal.

While in the embodiment of <FIG>, the optical enhancement device <NUM> is located at the light sensitive device <NUM> or embedded in the light sensitive device <NUM>, in other embodiments the optical enhancement device <NUM> is located at other locations, such as at the node <NUM> as shown in <FIG>. This allows for node-specific placement of optical enhancement devices <NUM> such that different optical enhancement devices <NUM> may be placed at different nodes <NUM>. Further, in some embodiments, combinations of optical enhancement devices <NUM>, such as combinations of bandpass filters and polarizers, may be utilized to filter or disseminate certain conditions of the scattered/reflected light. Further, in systems <NUM> where the nodes <NUM> include two or more cores <NUM>, <NUM>, optical enhancements <NUM> may be located at an individual core <NUM>, <NUM> or at two or more of the cores <NUM>, <NUM>.

Referring now to <FIG>, in some embodiments the system <NUM> includes focusing or expanding optical elements to increase range, sensitivity or field of view of the detection system <NUM> in detecting smoke/gas or other conditions or events. A focusing optical element can be placed at the node or between the control system and fiber harness to increase range and sensitivity by converging or collimating light. Also, an expanding optical element can be placed in similar locations to increase the field of view of the node by diverging the light. By way of example, optical elements may include mirrors, focusing lenses, diverging lenses, and diffusers, along with the integration of antireflective coatings on the optical elements or components thereof.

As shown in <FIG>, the optical elements may be one or more lenses <NUM> located at the node <NUM>. The lens <NUM> reduces divergence of the outgoing beam transmitted from the light source <NUM>, while also increasing the amount of scattered light accepted by the node <NUM> for transmission to the light sensitive device <NUM>. In some embodiments, the lens <NUM> is fused to the end of cores <NUM>, <NUM> at the node <NUM> to reduce scattering of the light off of the lens <NUM> face, thereby enhancing light collection efficiency of the node <NUM>. Further, in some embodiments, cores <NUM>, <NUM> may have lensed and tapered fibers, which do not require fusing and function as a lens <NUM>. In other embodiments, the lens <NUM> may be configured to reduce the scattering of light off of the lens face. Further, the lens <NUM> may include beam steering features, such as a solid state material which is utilized to change the refractive index of incident light to steer the light along the cores <NUM>, <NUM>. The beam steering feature may also be a photonic integrated circuit, which utilizes patterned silicon to control the directional emission of light.

Referring now to <FIG>, in some embodiments the optical elements may include a parabolic mirror <NUM> located at the node <NUM>. The parabolic mirror <NUM> is located off-angle relative to a node axis <NUM>. As with the lens <NUM>, the parabolic mirror <NUM> reduces divergence of the outgoing beam transmitted from the light source <NUM>, while also increasing an amount of scattered light accepted by the node <NUM> for transmission to the light sensitive device <NUM>. In some embodiments, the parabolic mirror <NUM> is configured to rotate about a rotational axis during operation of the system <NUM> to further increase a coverage area of the node <NUM>.

In some embodiments, both lens <NUM> and mirror <NUM> may be utilized at node <NUM>. Further, while in the embodiments illustrated in <FIG> and <FIG> optics are utilized at each node <NUM>, in other embodiments, optics may be utilized only at selected nodes <NUM> to provide their benefits to the selected nodes <NUM>, such as increasing detection range at selected nodes <NUM> due to, for example, constraints in placement of nodes <NUM> in the protected space. In other embodiments, the optical elements can be placed at the light source <NUM> or light sensitive device to enhance the detection system <NUM>.

In addition to smoke or dust, the system <NUM> may be utilized to monitor or detect pollutants such as volatile organic compounds (VOC's), particle pollutants such as PM2. <NUM> or PM10. <NUM> particles, biological particles, and/or chemicals or gases such as H<NUM>, H<NUM>S, CO<NUM>, CO, NO<NUM>, NO<NUM>, or the like. Multiple wavelengths may be transmitted by the light source <NUM> to enable simultaneous detection of smoke, as well as individual pollutant materials. For example, a first wavelength may be utilized for detection of smoke, while a second wavelength may be utilized for detection of VOC's. Additional wavelengths may be utilized for detection of additional pollutants, and using multiple wavelength information in aggregate may enhance sensitivity and provide discrimination of gas species from false or nuisance sources. In order to support multiple wavelengths, one or more lasers may be utlilized to emit several wavelengths. Alternatively, the control system can provide selectively controlled emission of the light. Utilization of the system <NUM> for pollutant detection can lead to improved air quality in the predetermined space <NUM> as well as improved safety.

In some embodiments, such as shown in <FIG>, the fiber optic branches <NUM> are each operably connected to the fiber harness backbone <NUM>, which may only include a single fiber optic core, via a coupling <NUM>. In some embodiments, the coupling <NUM> is one of a splice connection, a fused connection or a solid state switching device. Utilizing couplings <NUM> allows nodes <NUM> to be added to the fiber harness <NUM> after installation of the fiber harness <NUM>, or removal or relocation of the nodes <NUM> once the fiber harness <NUM> is installed. The couplings <NUM> therefore increase flexibility of the fiber harness <NUM> and the system <NUM>.

In another embodiment, such as shown in <FIG>, a first fiber optic core <NUM> is operably coupled to a first node <NUM>, while a second node <NUM> is operably coupled to a second fiber optic core <NUM>. In such embodiments, the first fiber optic core <NUM> is utilized for transmission of light from the light source <NUM>, while the second fiber optic core <NUM> receives scattered light and conveys the scatter light to the light sensitive device <NUM>. In some embodiments, a first coupling 132a coupling the first fiber optic core <NUM> to the first node <NUM> is the same as a second coupling 132b coupling the second fiber optic core <NUM> to the second node <NUM>, while in other embodiment the first coupling 132a is different from the second coupling 132b.

Further, as an alternative to or in addition to the splice connection, fused connections, one or more solid state switching devices, optical amplifiers <NUM> may be placed along the fiber harness <NUM> to amplify signals proceeding through the fiber harness <NUM>. The optical amplifier <NUM> may be located, for example as shown in <FIG>, between nodes <NUM>, or between the light detection device <NUM> and the fiber harness <NUM>. Further, in some embodiments, coupling <NUM> may be located at other locations along the fiber harness <NUM>, for example, between the fiber harness <NUM> and the light source <NUM>, and/or between the fiber harness <NUM> and the light sensitive device <NUM>. Referring now to <FIG>, the control system <NUM> is configured for multiple inputs and/or multiple outputs for communication of information through the fiber optic cables <NUM> and the nodes <NUM>. In some embodiments, the multiple inputs and outputs may include an internet connection <NUM>, a building network or management system <NUM>, and/or a fire panel <NUM> of the building or enclosed space. The fire panel <NUM> is configured for communications with, for example, a fire department, and/or is configured to transmit alarms through the building or space in the event of detection of smoke, fire or other substance by the system <NUM>. In the embodiment shown in <FIG>, the fiber optic cables <NUM> are further utilized for the communication of alarms, alerts and other information, such as system diagnostic information through the building. The control system <NUM> is able to both measure the condition in the predetermined area <NUM> and provide communication. For example, once the control system <NUM> determines that a condition is present based on detection signals received from one or more nodes <NUM>, the control system <NUM> transmits one or more alarm signals from the fire panel <NUM> along fiber optic cables <NUM> to one or more alarm units <NUM> in the building or space which initiate an alarm or alert based on the received alarm signals. The control system <NUM> is able to do this in a fiber optic harness <NUM> by combining frequency and amplitude modulation of the light. In some embodiments, the alert or alarm is an audible sound or sounds, while in other embodiments the alert or alarm is a light, or a combination of light and sound. Further, the control system <NUM> may be configured to send and/or receive communication through the fiber optic cables <NUM> and the nodes <NUM> to communicate with one or more building infrastructure or local devices in the space via modulated light transmitted along the cables <NUM>. In some embodiments, this communication is via Li-Fi protocol.

Claim 1:
A detection system (<NUM>) for measuring one or more conditions within a predetermined area comprising:
a fiber harness (<NUM>) having at least one fiber optic cable (<NUM>) for transmitting light, the at least one fiber optic cable defining a node (<NUM>) arranged to measure the one or more conditions;
a light source (<NUM>) coupled to the at least one fiber optic cable for emitting a modulated light to the node, the modulated light being transmitted into the predetermined area;
a light sensitive device (<NUM>) coupled to the at least one fiber optic cable for receiving light scattered within the atmosphere adjacent the node; and
a control unit (<NUM>) operably coupled to the light source and to the light sensitive device and configured to determine at least one of a presence and magnitude of the one or more conditions within the predetermined area;
characterised in that
the light source is configured to be selectively operated to generate modulated light in a specific pattern;
wherein determining at least one of a presence and magnitude of the one of more conditions within the predetermined area includes computing a cross-correlation of the light received by the light sensitive device with a second specific pattern;
wherein the light within the specific pattern varies in at least one of intensity, width, frequency, and phase; and
wherein the one or more conditions include smoke caused by a fire and presence of a person.