Number Of Optical Signals Research Articles

The application of fluorescent optical fiber in partial discharge detection of Ring Main Unit

Ring Main Units (RMU) are commonly used in the power system. At present, there is no example of partial discharge (PD) detection in RMU by optical method. In this article, the PD in RMU was detected by optical method. Meanwhile, the characteristics of the optical signals and the influential factors have been analyzed. The phase, amplitude and quantity characteristics of the PD optical signals in the positive and negative half cycle was analyzed and listed and we can find the PD optical signals under four typical insulating defects have their own characteristics; if the output of the PMT have not reach it saturation value, the maximum amplitude of the optical signals will increase with the increase of the applied voltage while the average amplitude of the optical signals did not always increase except the insulation gap defect; besides, the number of the optical signals also have a positive relationship with the applied voltage. When the optical receiving length quadruple, the initial PD voltage (IPDV) of optical method has decreased about 14.7% while the number of PD optical signals has increased about 1046.5%; when the pressure changing from 0.1 MPa to 0.14 MPa, the IPDV has increased about 83.65% while the signals number has decreased about 36.23%; when the distance between the optical fiber and the defect model changing from 2.5 cm to 7.5 cm, the IPDV has increased about 9.3% while the signals number has decreased about 65.7%.

A study of digital optical signal multiplexing technique using short pulse amplitude modulation

AbstractAs an optical multiplexing system to be applied to the uplink of a passive optical network, the authors propose short pulse amplitude modulation as a form of optical CDM. Although this method has the attractive feature that no timing control and wavelength control is necessary, the number of multiplexed optical signals is limited by the optical beat interference. In this paper, the signal‐to‐noise ratio and the number of optical signals that can be multiplexed are theoretically discussed when digital signals are transmitted with short pulse amplitude modulation in the case where the DFB‐LDs with identical wavelengths are used as the optical sources and the optical beat interference is generated within the signal bandwidth. It is found that the number of optical signals that can be multiplexed is 8 when the signal speed is 100 Mb/s and the amount of chirp in the LD is 280 MHz/mA. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(4): 35–41, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10075

Increasing acceptable number of signals in subcarrier multiple access optical networks in the presence of high optical beat interference

This paper theoretically and experimentally demonstrates that our proposed method improves the carrier-to-noise ratio (CNR) of subcarriers and significantly increases the number of acceptable optical signals in subcarrier multiple access (SCMA) systems using distributed feedback laser diodes (DFB-LD's) with the same center optical frequency. This method reduces optical beat interference by using the multiplied product of the subcarriers and a low-frequency signal. From the experimental results using 1.3 /spl mu/m DFB-LD's, the CNR sufficiently satisfies the required level even if the number of optical signals is three. Theoretically, the number of acceptable optical signals increases as LD's with wider optical line-width or with greater chirp coefficient are used. For example, assuming a laser chirp coefficient of 540 MHz/mA, the maximum number of LD's that can be used while still meeting the minimal CNR requirement is 12. This number corresponds to 66 optical beat interferences. Thus, this proposed beat-interference reduction technique is very effective in SCMA systems using DFB-LD's without optical frequency control.