MICRO-SENSOR NETWORKS

ABSTRACT The concept of an all-fiber, IC-based sensor network is presented. Fundamental issues including topology tradeoffs, powerbudget, and power distribution subsystem are analyzed. Some potential applications of such sensor networks are discussed. INTRODUCTION Each year, the airline industry spends billions of dollars on structure condition tests. The same test is normally required to berepeated several times during the lifetime of an airplane, and the frequency of the test is normally required to be increased asthe airplane gets older, but still some structures fail before the next scheduled test is performed. Many of these tests can notdetect internal degradation/damage in the structure, because normally only the surface of the structure is available for a test.These problems are also shared by users of many other large structures such as bridges, buildings, ships, and spacecraft,pipelines, ... etc. In space and under the sea, performing such tests can be also very expensive or nearly impossible. As aresult, there is a need for a built-in, real-time, structure monitoring system that can constantly monitor the condition of bothinside and outside of a structure and issue a real-time warning as a test result indicates the monitored structure is about tofail.A network of sensors distributed over the strategic locations in a structure is one of the solutions to the structure monitoringproblem. To reliably and accurately detect a potential structure failure, multiple sensor types may be needed. For example,strain gauges may provide a history of the net force exerted on various points in the structure, chemical sensors may provideinformation about corrosion by sensing the chemical released during the corrosion process. By comparing the results with themechanical limit and chemical properties of the structure, and correlating these two different data sets, the safety status of thestructure can be more accurately determined. To cover all the strategic points in a large structure, thousands of sensors andwires may be needed. It is advantageous to integrate all the sensor types together at a given point and transmit all the sensordata through the same transmitter. The sensor network should also be fault-tolerant to reduce the need for maintenance,because in some applications the sensor network may be embedded in the structure and is inaccessible to service. In someenvironments, the network should also be immune to corrosion and electromagnetic interference (EMI) and in some otherenvironments, the network may be required not to generate EM fields that could interfere with other EMI-sensitive devices.Hence, how to reliably and compactly network the sensor nodes together become two very important issues in designing thesensor network.