前言

光模塊因為有數字診斷監控功能（DDM, Digital Diagnostic monitoring）這位醫生進行實時的性能監測，能夠精確的找到故障位置，以及通過兼容性驗證直觀的反映不兼容的情況，所以其穩定性和可靠性得以提高。那么數字診斷監控功能又是如何修煉出這么強大的功能呢？通過內校準和外校準！

一、DDM的內校準

內校準：采用內部校準，A / D的值被校準為標準值，A / D轉換值經過物理量變換和相應縮放，最后輸出的數字標定值符合協議中規定的數值范圍。

A2區定義

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的外校準

外校準：采用外部校準時，存儲的是未經處理的A / D轉換值，監測軟件通過讀取存儲單元A2H中38H~5FH地址內的校準常數，再通過外部校準公式把A / D值換算成實際值

外部校準運算法則：

• 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