相对强度噪声(rin)测量程序[科学书苑]

Relative intensity noise (RIN) measuring procedure相对强度噪声（RIN）测量程序This procedure describes a component test which may not be appropriate for a system level test depending on the implementation.这是一个组件测试流程，根据应用环境来看，它可能不适合于系统级的测试。A.5.1 Test objective 测试目标When lasers which are subject to reflection induced noise effects are operated in a cable plant with a low optical return loss the lasers will produce an amount of noise which is a function of the magnitude and polarization state of the reflected light.当受到反射引起的噪声影响的激光器在具有低光回损的电缆设备中工作时，激光器将产生一定量的噪声，这个噪声是反射光的大小和偏振态的函数。The magnitude of the reflected light tends to be relatively constant. However, the polarization state varies significantly as a function of many cable parameters, particularly cable placement.反射光的大小趋于相对恒定。然而，偏振态受许多电缆参数的影响而呈现出一定的函数关系，特别是随电缆的放置而显著变化。In a cable plant which is physically fixed in place the variation is slow. If the fibre is subject to motion, such as occurs in a jumper cable, the change may be sudden and extreme. The effect is unpredictable changes in the noise from the laser with the result that the communication link may exhibit sudden and unexplainable bursts of errors.在固定的电缆设备中，变化是缓慢的。如果光纤被移动，例如跳线，则可能会有突然或剧烈的变化。从而造成激光器噪声的不可预知的变化，结果是通信链路可能表现出突然和无法解释的错误。The solution to this is to assure that the lasers used do not generate excessive noises under conditions of the worst case combination of polarization and magnitude of reflected optical signal.对此的解决方案是确保所使用的激光器在反射光信号的偏振态和大小的最坏组合的情况下不会产生过多的噪声。The noise generated is a function of the return loss of the cable plant. For the Fibre Channel the specified return loss is 12 dB resulting in the notation of RIN12 for the relative intensity noise.产生的噪声是电缆设备回波损耗的函数。对于光纤通道，规定的回波损耗为12 dB，所以相对强度噪声用符号RIN12来表示。放大器电功率计电流检测装置单模光纤被测设备/器件 偏振旋转器探测器偏置输入低通滤波器A.5.2 General test description 一般测试描述The test arrangement is shown in figure A.2 The test cable between the Device Under Test (DUT) and the detector forms an optical path having a single discrete reflection at the detector with thespecified optical return loss. There must be only one reflection in the system as the polarization rotator can only adjust the polarization state of one reflection at a time.测试装置如图A.2所示。被测设备（DUT）和探测器之间用测试电缆（光纤）相连，使其形成一条光路，在指定的回损范围内，探测器处会有一个离散的反射。偏振旋转器一次只能调整一个反射的偏振态，因此系统中只能有一个反射。Two measurements are made by the photo detector. The average optical power is determined by measuring the average current, Ipd, through the detector. The second measurement is the noise, which is measured by AC coupling the detector into the high frequency electrical power meter. Ifneeded, an amplifier may be used to boost the signal to the power meter.两个测量值由光电探测器进行测量。平均光功率是通过测量探测器的平均电流Ipd来确定。第二个测量值是噪声，它是通过将探测器交流耦合到高频电功率计中测量的。如果需要时，可以使用放大器来增强输入功率计的信号。A low pass filter is used between the photo-detector and the power meter to limit the noise measured to the pass band appropriate to the data rate of interest. In order to measure the noise the modulation to the DUT must be turned off. If the laser is modulated the modulation power will be measured by the power meter rather than the noise power.在光电探测器和功率计之间使用低通滤波器，以将测量的噪声限制在适合测量的数据速率的通带。为了测量噪声，必须关闭对DUT的调制。如果激光器被调制，则功率计会测量到更大的调制功率而非噪声功率。A.5.3 Component descriptions 组件描述Test Cable 测试电缆The test cable and detector combination must be configured for a single dominate reflection with an optical return loss of 12dB. (The Optical return loss may be determined by the method of FOTP-107) If multiple lengths of cable are required to complete the test setup they should be joined with splices or connectors having return losses in excess of 30dB. The length of the test cable is not critical but should be in excess of 2 m.测试电缆和探测器组合必须配置为单回路反射，光回波损耗为12dB。 （光学回波损耗可以通过FOTP-107的方法来确定）如果需要多根电缆来完成测试设置，则应该使用回波损耗超过30dB的接头或连接器。测试电缆的长度并不重要，但应超过2米。Polarization Rotator 偏振旋转器The polarization rotator must be capable of transforming an arbitrary orientation elliptically polarized wave into a fixed orientation linearly polarized wave. A polarization rotator consisting of two quarter wave retarders will have the necessary flexibility. A possible construction technique is given in LeFevre, 1980 3.偏振旋转器必须能够将任意定向的椭圆偏振波转换成固定方向的线偏振波。所以该偏振旋转器将需要两个四分之一波片来使其具有必要的灵活性。 LeFevre，1980 3中给出了一种可能的结构模型。Detector and Detector/Amplifier 探测器和探测器/放大器The detector may be of any type which is sensitive to the wavelength range of interest. The frequency response of the detector must be higher than the cut-off frequency of the low pass filter.探测器可以是对相应（DUT）波长范围敏感的任何类型，探测器的频率响应必须高于低通滤波器的截止频率。The detector should be capable of determining the average and variation of the optical signal. Typically the average optical power is determined by the current, Id, through the diode. The detector assembly should have an effective output impedance of 50. If necessary, the noise may be amplified to a level consistent with accurate measurement by the power meter.探测器应当能够确定光信号的平均值和变化量。一般的，平均光功率由通过二极管的电流Id确定。探测器组件的等效输出阻抗应为50。如有必要，噪声可以放大到与功率计测量精度一致的水平。Filter滤波器The low pass filter should have a 3dB bandwidth of approximately 75% of the bit rate. Recommended values are shown in table A.1. The total filter bandwidth used in the RIN calculation must take the low frequency cut-off of the d.c. blocking capacitor into consideration.低通滤波器应该具有约为比特率75的3dB带宽。表A.1列出了推荐值。在RIN计算中使用的总滤波器带宽考虑到隔直电容必须采取直流的低频截止。The filter should be placed in the circuit as the last component before the power meter so that any high frequency noise components generated by the detector/amplifier are eliminated. If ensure that the filter does not lose its rejection at extremely high frequencies.滤波器应作为功率计之前的最后一个元件放置在电路中，以免探测器/放大器产生的任何高频噪声成分被消除。如果所使用的功率计具有非常宽的带宽，则应谨慎选择滤波器，以确保滤波器在极高频率下不会失去其抑制性能。Power Meter功率计The power meter should be an RF type designed to be used in a 50 coaxial system. The meter must be capable of being zeroed in the absence of input optical power to remove any residual noise from the detector or its attendant amplifier, if used.功率计应该是RF类型，设计用于50同轴系统。在没有输入光功率的情况下，仪表必须能被清零，以去除探测器或其伴随的放大器（如果使用的话）的任何残余噪声。A.5.4 Test Procedure测试程序a) Connect and turn on the test equipment. Allow the equipment to stabilize for the manufacturers recommended warm up time.连接并打开测试设备，让设备经过制造商建议的预热时间后达到稳定。b) With the DUT disconnected zero the power meter to remove the contribution of any noise power from the detector and amplifier, if used.在DUT断开的情况下将功率计调零以消除来自检测器和放大器（如果使用的话）的任何噪声功率的干扰。c) Connect the DUT, turn on the laser and verify that the optical output power is at the average power appropriate for the DUT by means of the detector current. The laser should not be modulated.连接被测器件，打开激光器，通过监控工作电流使光器件工作在其平均光功率附近，激光不应被调制。d) Operate the polarization rotator while observing the power meter output to maximize the noise read by the power meter.在观察功率计输出的同时操作偏振旋转器，以记录功率计读取的噪声最大值。e) Calculate RIN from the observed detector current and electrical noise by use of the equation:利用下式计算观测到的探测器电流和电噪声的RIN：Where:其中 RIN = Relative Intensity NoiseRIN = 相对强度噪声Ipd = Current through the detector (A)Ipd = 通过探测器的电流（A）Pe = Electrical noise power in WattsPe = 电噪声功率，单位为瓦特BW = Noise Bandwidth of the measuring system (Hz)= Low Pass Bandwidth of filter - High Pass Bandwidth of DC blocking capacitorBW = 噪声测量系统的带宽（Hz）= 滤波器的低通带宽 - 隔直电容的高通带宽25 = Effective Load Impedance (50 ohm load in parallel with a 50 ohm power meter)25 = 有效负载阻抗（与50欧姆功率计并联的50欧姆负载）G = Gain in dB of any amplifier in the Noise Measurement pathG = 噪声测量路径中任何放大器的以dB为单位的增益5互联b类