Umbilical Communications Condition Monitoring

Abstract

Abstract Umbilical communication utilising optical fibre has increased in recent years, however communication via an electrical umbilical still dominate the industry. When communicating over electrical conductor’s modulation techniques such as Orthogonal Frequency Division Multiplexing (OFDM) and Quadrature Amplitude Modulation (QAM) can be used to improve data rate and reduce transmission errors. These modulation technologies lend themselves to condition monitoring approaches that do not affect the performance of the communication channel. Here we present a condition monitoring system to detect in real time umbilical communications deterioration before failure. The Aker Solutions electrical communications modem utilise OFDM or QAM techniques to encode digital data such that a particular phase and amplitude represent a binary code. These data can be represented graphically where a particular phase and amplitude are shown as locations on a XY graph (constellation diagram). Noise, communication channel interference, or any other factor reducing communication channel performance will result in a move away (an error vector) from the ideal location on the constellation diagram. The QAM data also contain pilot tones transmitted at know amplitudes and frequencies to enhance modem performance. These pilots can be utilised to produce a frequency response of the umbilical communication channel. For condition monitoring the error vector and channel frequency response can be utilised to determine the end-to-end health of the communication channel. The communications modem is capable of fault free operation with large error vectors and poor channel frequency response. Therefore, the user may not be aware of deterioration in umbilical performance until the communication channel fails. The ability to monitor the condition of umbilical communications in real time without affecting data throughput presents a significant advantage. Enabling the user to detect and correct umbilical communications problems before failure. This paper will present results from trials using the umbilical condition monitoring system on QAM16 communications over a Research and Development umbilical simulator.