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digital diagnostic monitoring (ddm) Introduction
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WHITE PAPER
Fiberstore White Paper | Digital Diagnostic Monitoring Introduction
Cisco announced the end of sale of its SFP transceiver Cisco GLC-SX-MM transceiver and published areplacement—Cisco GLC-SX-MMD transceiver. The module numbers of the two transceiver onlydiffer in one letter “D”. This “D” mainly represents a function of Cisco GLC-SX-MMD transceiver andis inherited by most of optical transceivers offered today. It is the main reason why CiscoGLC-SX-MMD transceiver can replace its predecessor. What is this “D”? Why the GLC-SX-MMD canreplace GLC-SX-MM? This article is to offer the answers to these questions.
What is Digital Diagnostic Monitoring (DDM)?“D” in GLC-SX-MMD represents the DDM function which is short for digital diagnostic monitoringaccording to the industry standard MSA (Multi-Source Agreement) SFF-8472 and is also known asDOM (Digital Optical Monitoring). When buy fiber optic transceiver today, you will have the optionwith or without DDM/DOM. And most of the modern transceivers are with the DDM function. Thistechnology allows the user to monitor real-time parameters of the fiber optic transceivers, likeoptical input/output power, temperature, laser bias current, and transceiver supply voltage, etc.
What Can Digital Diagnostic Monitoring Do?Literally, DDM function can provide component monitoring on transceiver applications in details.However, DDM’s application is not limited to this. The SFF-8472 added DDM interface and outlinedthat DDM interface is an extension of the serial ID interface defined in GBIC specification, as well asthe SFP MSA. DDM interface includes a system of alarm and warning flags which alert the hostsystem when particular operating parameters are outside of a factory set normal operating. Thus,DDM interface can also enable the end user with the capabilities of fault isolation and failureprediction. This part is to illustrate what can be done with DDM.
Component Monitoring: The DDM enables the end user to monitor key parameters in theperformance of the fiber optic transceiver including the following: Transceiver temperature Transceiver supply voltage Laser bias current Transmit average optical power Received optical modulation amplitude (OMA) or Average Optical Power
Digital DiagnosticMonitoring Introduction
WHITE PAPER
Fiberstore White Paper | Digital Diagnostic Monitoring Introduction
The real-time diagnostic parameters can be monitored to alert the system when the transceiver’sspecified operating limits are exceeded and compliance cannot be ensured.
Fault isolation: The DDM function can be used to isolate the particular location of fault in fiber opticnetwork system. Combining the DDM interface status flags, transceiver hard pins and diagnosticparametric monitor data the specific location and cause of a link failure can be pinpointed.
Failure prediction: The DDM can also be used to help in failure prediction on fiber optic links, whichis based on the transceiver parametric performance. Although, this application is not yet fullymature, but there is still room for improvement. There are two basic types of failure conditions thatcan be seen on fiber optic transceivers:
Device faults—A device non-operation or malfunction. Typically applied more to transmitterperformance, due to nature of semiconductor lasers.
High error rate conditions—Operating conditions are such that transceiver is operating at itssignal-to-noise limit. Applies more to fiber optic receiver performance.
Providing parameter monitoring, fault isolation, and failure prediction, fiber optic transceivers withDDM help to ensure that the business can be proactive in preventative maintenance of the networkand ensure business continuity. And it would easy to explain why modern transceivers are withDDM and why GLC-SX-MMD can replace GLC-SX-MM. It is irresistible development trend of industryand technology.
What should be mentioned is that although optical transceivers with DDM are much popular thanthose without DDM, some user still use the older optical transceivers in consideration of theupgrading costs. To satisfy the customers’ needs, optical transceivers with DDM and without DDM
WHITE PAPER
Fiberstore White Paper | Digital Diagnostic Monitoring Introduction
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Notice: This document is for informational purposes only and does not set forth any warranty, expressed orimplied, concerning any equipment, equipment features, or service offered or to be offered by Fiberstore.Fiberstore reserves the right to make changes to this document at any time, without notice, and assumes noresponsibility for its use. This information document describes features that may not be currently available.Contact a Fiberstore sales team for information on feature and product availability.
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