DDM的修炼手册

前言

光模块因为有数字诊断监控功能（DDM, Digital Diagnostic monitoring）这位医生进行实时的性能监测，能够精确的找到故障位置，以及通过兼容性验证直观的反映不兼容的情况，所以其稳定性和可靠性得以提高。那么数字诊断监控功能又是如何修炼出这么强大的功能呢？通过内校准和外校准！

一、DDM的内校准

内校准：采用内部校准，A / D的值被校准为标准值，A / D转换值经过物理量变换和相应缩放，最后输出的数字标定值符合协议中规定的数值范围。

A2区定义

A2h	Bit	Name	Description
96	All	Temperature MSB	Internally measured module temperature
97	All	Temperature LSB
98	All	Vcc MSB	Internally measured supply voltage in transceiver
99	All	Vcc LSB
100	All	TX Bias MSB	Internally measured TX Bias Currnet
101	All	TX Bias LSB
102	All	TX Power MSB	Measured TX output power
103	All	TX Power LSB

A2h	Bit	Name	Description
104	All	RX Power MSB	Measured RX input power
105	All	RX Power LSB
106	All	Optional Laser Tem/Wavelength MSB	Measured laser temperature or wavelength
107	All	Optional Laser Tem/Wavelength LSB
108	All	Optional TEC current MSB	Measured TEC current(positive is cooling)
109	All	Optional TEC current LSB

二、DDM的外校准

外校准：采用外部校准时，存储的是未经处理的A / D转换值，监测软件通过读取存储单元A2H中38H~5FH地址内的校准常数，再通过外部校准公式把A / D值换算成实际值

外部校准运算法则：

• T(C) = Tslope * TAD (16 bit signed twos complement value) + Toffset. The result is in units of 1/256C。
• V(uV) = VSLOPE * VAD (16 bit unsigned integer) + VOFFSET. The result is in units of 100uV
• I (uA) = ISLOPE * IAD (16 bit unsigned integer) + IOFFSET. This result is in units of 2 uA
• TX_PWR (uW) = TX_PWRSLOPE * TX_PWRAD (16 bit unsigned integer) + TX_PWROFFSET. This result is in units of 0.1uW
• Rx_PWR (uW) = Rx_PWR(4) * Rx_PWRAD4 (16 bit unsigned integer) +Rx_PWR(3) * Rx_PWRAD3 (16 bit unsigned integer)+Rx_PWR(2) * Rx_PWRAD2 (16 bit unsigned integer)+Rx_PWR(1) * Rx_PWRAD (16 bit unsigned integer) +Rx_PWR(0). The result is in units of 0.1uW