光收發(fā)模塊DDM功能介紹

1、光收發(fā)模塊DDM功能介紹 -夏致富 QQ:706336149 手機、 DDM定義 DDM(數字診斷監(jiān)視功能)means digital diagnostic monitoring, define in SFF-8472 documents. 監(jiān)測的5個實時測量參數為： 模塊溫度temp 工作電壓Vcc 激光器偏流Laser Bias 接收光功率Rx_power 發(fā)射光功率Tx_power 1、DDM的實現流程 讀取 5個監(jiān)控量參數經過A/D轉換，將模擬量轉換為數字量。通過內部校準或外部校準， 將監(jiān)測的校準值或外部校準系數寫入內存中(E2ROM)。 2、DDM功能的應用

2、 通信的一個重要指標就是要保證通信數據傳輸正確，也就是不能產生誤碼，在產生誤碼的情況下就要重新建立數據鏈接。但是模塊在使用的過程中會出現其他因素影響模塊的功能使得通信數據出現錯誤，比如：模塊的使用溫度、光纖的曲折影響光功率、模塊本身的使用壽命。傳輸者不能把有誤碼的數據也傳送給接收者，同樣做為接收信號的一方也不能把有誤碼的信號拿來使用。這樣就需要知道模塊當前的運行狀況，以使模塊在正常的工作條件下傳輸數據。于是就需要連續(xù)（間隔一定時間）的監(jiān)視模塊當前的狀況，也就是監(jiān)測上面所說的5個指標。然后將監(jiān)測到的值對比模塊在正常工作條件下所要求的范圍。如果不在范圍之類就報警，顯示模塊處在不良狀況下，交換機就會

3、停止發(fā)送數據，同樣作為接收信息一方拒絕接收數據。直到模塊正常工作狀況下重新發(fā)送/接收數據。同時,如果光網絡數據鏈路出現問題,可以幫助系統(tǒng)管理員找出光纖鏈路中發(fā)生故障的位置，簡化維護工作，提高系統(tǒng)的可靠性。模塊使用時間預測模塊使用時間預測智能帶DDM的SFP提供了一種預測激光器劣化的實時的參數監(jiān)測手段。光模塊內部的光功率反饋控制單元會將輸出功率控制在一個穩(wěn)定的水平上，但是，隨著激光器的老化，激光器的量子效率會降低。功率的控制是通過提高激光的偏置電流（Tx_Bias）來實現的。因此，我們可以通過監(jiān)測激光的偏置電流來預測激光器的壽命。這種方法可粗略的估計激光器的使用壽命是否接近終了。因為激光的偏置電

4、流與模塊的工作溫度及工作電壓都有關系，所以在設定偏置電流極限時需要考慮Temp和Vcc的影響。通過對收發(fā)模塊內部的工作電壓和溫度進行實時監(jiān)測，可以讓系統(tǒng)管理員發(fā)現一些潛在的問題：1）Vcc電壓過高，會帶來CMOS器件的擊穿；Vcc電壓過低，激光器不能正常工作。2）接收功率太高，會損壞接收模塊。3）工作溫度太高，會加速器件的老化。此外，通過對接收到的光功率的監(jiān)測，可以對線路和遠端發(fā)射機的性能進行監(jiān)控。 這種故障預測可以使網絡管理人員在系統(tǒng)性能受到影響之前找到潛在的鏈路故障。通過故障預告，系統(tǒng)管理員可以將業(yè)務切換到備份鏈路上或者替換可疑器件，從而在不間斷業(yè)務的情況下修復系統(tǒng)。 故障定位故障定位在光

5、鏈路中，定位故障的發(fā)生位置對業(yè)務的快速加載至關重要。故障隔離特性則可以使系統(tǒng)管理員快速定位鏈路故障的位置。此特性可以定位故障是在模塊內還是在線路上；是在本地模塊還是在遠端模塊。通過快速定位故障，減少了系統(tǒng)的故障修復時間。故障定位中，需要綜合分析狀態(tài)位，管腳和測量參數。總之，通過數字診斷功能，可以定位故障。在故障定位中，需要對Tx_power，Rx_power， Temp，Vcc，Tx_Bias的警告和告警狀態(tài)進行綜合分析。內存鏡像中的狀態(tài)變量Tx Fault和Rx LOS (信號丟失)都對故障的分析起著重要的作用。兼容性驗證兼容性驗證數字診斷的另一個功能是模塊的兼容性驗證。兼容性驗證就是分析模

6、塊的工作環(huán)境是否符合數據手冊或和相關的標準兼容。模塊的性能只有在這種兼容的工作環(huán)境下才能得到保證。在有些情況下，由于環(huán)境參數超出數據手冊或相關的標準，將造成模塊性能下降，從而出現傳輸誤碼。工作環(huán)境與模塊不兼容的情況有：1）電壓超出規(guī)定范圍；2）接收光功率過載或低于接收機靈敏度；3）溫度超出工作溫度范圍。3、DDM-SFF-8472 在SFF-8472 MSA中，規(guī)范了數字診斷功能及有關SFF-8472的詳細內容。該規(guī)范規(guī)定，在模塊內部的電路板上監(jiān)測和數字化參數信號。然后，提供經過標定的結果或提供數字化的測量結果及標定參量。這些信息被存貯在標準的內存結構中，以便通過兩線串行接口讀取。SFF-84

7、72保留了原來SFP/GBIC在地址A0h處的地址映射，并在地址A2h處又新增了一個256字節(jié)的存貯單元。這個存貯單元除了提供參數監(jiān)測信息外，還定義了報警標志或告警條件，各個管腳的狀態(tài)鏡像，有限的數字控制能力和用戶可寫的存儲單元。 The enhanced interface uses the two wire serial bus address 1010001X (A2h) to provide diagnostic information about the modules present operating conditions.The transceiver generates th

8、is diagnostic data by digitization of internal analog signals. Calibration and alarm/warning threshold data is written during device manufacture.Digital Diagnostic Memory Map Specific Data Field Descriptions Diagnostics: Data Fields Address A2h二、DDM功能Diagnostics Overview Address A2h 2 wire serial bu

9、s address 1010001X (A2h) is used to access measurements of transceiver temperature, internally measured supply voltage, TX bias current, TX output power, received optical power, and two additional quantities to be defined in the future. The values are interpreted differently depending upon the optio

10、n bits set at address 92. If bit 5 “internally calibrated” is set, the values are calibrated absolute measurements, which should be interpreted according to the section “Internal Calibration” below. If bit 4 “externally calibrated” is set, the values are A/D counts, which are converted into real uni

11、ts per the subsequent section titled “External Calibration”. Measured parameters are reported in 16 bit data fields, i.e., two concatenated bytes. The 16 bit data fields allow for wide dynamic range. This is not intended to imply that a 16 bit A/D system is recommended or required in order to achiev

12、e the accuracy goals stated below. The width of the data field should not be taken to imply a given level of precision. It is conceivable that the accuracy goals herein can be achieved by a system having less than 16 bits of resolution. It is recommended that any low-order data bits beyond the syste

13、ms specified accuracy be fixed at zero. Overall system accuracy and precision will be vendor dependent. To guarantee coherency of the diagnostic monitoring d a t a , t h e h o s t i s r e q u i r e d t o r e t r i e v e a n y multi-byte fields from the diagnostic monitoring data structure (IE: Rx Po

14、wer MSB - byte 104 in A2h, Rx Power LSB - byte 105 in A2h) by the use of a single two-byte read sequence across the two-wire interface. The transceiver is required to ensure that any multi-byte fields which are updated with diagnostic monitoring data (e.g. Rx Power MSB - byte 104 in A2h, Rx Power LS

15、B - byte 105 in A2h) must have this update done in a fashion which guarantees coherency and consistency of the data. In other words, the update of a multi-byte field by the transceiver must not occur such that a partially updated multi-byte field can be transferred to the host. Also, the transceiver

16、 shall not update a multi-byte field within the structure during the transfer of that multi-byte field to the host, such that partially updated data would be transferred to the host. Accuracy requirements specified below shall apply to the operating signal range specified in the relevant standard. T

17、he manufacturers specification should be consulted for more detail on the conditions under which the accuracy requirements are met.Internal Calibration Measurements are calibrated over vendor specified operating temperature and voltage and should be interpreted as defined below. Alarm and warning th

18、reshold values should be interpreted in the same manner as real time 16 bit data.Converted analog values. Calibrated 16 bit data.External Calibration Measurements are raw A/D values and must be converted to real world units using calibration constants stored in EEPROM locations 56 95 at 2 wire seria

19、l bus address A2h. Calibration is valid over vendor specified operating temperature and voltage. Alarm and warning threshold values should be interpreted in the same manner as real time 16 bit data.Alarm and Warning Flags Address A2h, Bytes 112-117 Bytes 112 117 contain an optional set of alarm and

20、warning flags. The flags may be latched or non-latched. Implementation is vendor specific, and the vendors specification sheet should be consulted for details. It is recommended that in either case, detection of an asserted flag bit should be verified by a second read of the flag at least 100ms late

21、r. For users who do not wish to set their own threshold values or read the values in locations 0 - 55, the flags alone can be monitored. Two flag types are defined. Alarm and Warning ThresholdsAlarm and Warning Flag Bitscontinuation ：三、DS1859實現DDM功能 The DS1859 dual, temperature-controlled, nonvolati

22、le(NV) variable resistors with three monitors consists oftwo 50k or two 20k, 256-position, linear, variableresistors; three analog monitor inputs (MON1, MON2,MON3); and a direct-to-digital temperature sensor. Thedevice provides an ideal method for setting and temperature-c o m p e n s a t i n g b i

23、a s v o l t a g e s a n d c u r r e n t s i ncontrol applications using minimal circuitry. The variabler e s i s t o r s e t t i n g s a r e s t o r e d i n E E P R O M m e m o r ya n d c a n b e a c c e s s e d o v e r t h e 2 - w i r e s e r i a l b u s .Memory Organization, ADEN = 1If the ADEN bit is 1, additional 128 bytes of EEPROMare accessible through the Main Device, selected asT a b l e 0 0 ( s e e F i g u r e 3 ) . I n t h i s c o n f i g u r a t i o n , t h eAuxiliary Device is not accessible. APEN controls theprotect