What is DDM and DOM used in Optical SFP/SFP+ Transceivers?

What is DDM (Digital Diagnostic Monitoring)?

DDM or Digital Diagnostic Monitoring is a management technology which allows operators to monitor several parameters of a fibre optic transceiver, such as optical input/output levels, temperature, laser bias current and supply voltage. All of these parameters can be monitored in real-time.

Examples of optical modules supporting DDM are the Small Form Factor Pluggable modules such as SFP and SFP+ for 1Gbps to 10Gbps and up to 25Gbps capacity

SFP / SFP+ Optical Module with DDM / DOM Monitoring features
SFP module with DDM / DOM Feature

What does the DDM do exactly?

DDM is capable of providing component monitoring on transceiver applications in great detail. The system that is used is an extension of the interface defined in GBIC specification (GBIC being a type of transceiver).

The interface itself is capable of generating alarms and warning flags which alert the host system when operating parameters fall outside of a set of ‘normal operating’ rules. This allows the end user to isolate faults and predict failure.

What is DOM?

DOM or Digital Optical Monitoring is used to monitor certain parameters of an optical transceiver in real-time. This helps operators to identify the location of a fiber link failure which in turn helps to simplify the maintenance process and improve overall system reliability.

DOM gives you the ability to monitor the transmit and receive power of the optical transceiver module, its temperature and supply voltage. Each system can be configured to monitor transceivers that are in operation either globally or by specific port.

With DOM console message and syslog messages are sent if operation falls below or rise above the specific transceivers manufacturer thresholds.

Most modern transceivers support DOM functions.

Schematic diagram of Optical SFP/SFP+ module with DDM / DOM features
Schematic diagram of Optical SFP/SFP+ module with DDM / DOM features available on the (0) (1) and (2) pins

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The Real Cost of Fiber Cuts: How to solve using Gigabit Wireless

Fiber Cuts – The Real Cost – How to solve using Gigabit Wireless

Fibre Optic Cable - Fibre Cuts cost time and moneyOften you can’t avoid fiber cuts: they happen on public land or under public streets, outside your control.  The vast majority of corporate LAN connections, cable, Internet and LTE backhaul, is done over fiber optic cable.   In one report CNN stated that about 99 percent of all international communications occur over undersea cabling. Alan Mauldin, research director at U.S.-based research firm Telegeography, noted that while some major cabling projects can come with high price tags, fiber optics is considered more robust and more cost-effective than common wireless alternatives like satellite.

Gigabit Wireless solves Fibre Cut outagesBut while fiber optic cabling is traditionally seen as the safer option, that may be a misconception.  When installed correctly, fiber optics is the “perfect” media, transmitting Gigabits of data without interruption.  However, any disruption to the fragile fiber causes data outages which take days or weeks to locate and repair. According to data from the Federal Communications Commission. about a quarter of all network outages that happened between 1993 and 2001 were from cables being cut. Regardless of how the fiber cut occurred, such outages can be particularly damaging.

How easy is it to repair a fiber cut?

Fiber is not a “self healing” media: skilled teams with specialist fiber-splicing and terminating equipment are required to repair a broken fiber connection.  Most data communication engineers do not have this equipment or training on using them. fiber repair is a specialist business and getting trained people and splicing equipment to site costs time and money.  Factoring the anticipated cost of a fiber repair into a budget for “downtime” and “unproductivity” for corporates – and missing SLA’s for uptime for Service Providers – is a serious issue, including business continuity planning.  For rural areas, access to sites can be limited, with some locations limited by poor weather, and for islands sometimes only with infrequent access by sea or air.

Common causes of fiber cut outages

As these instances show, there are many different ways in which fiber optic cabling can be disrupted:

By vandalism – This type of fiber cut outage has been worryingly common of late. According to CNN, there have been 11 separate incidents involving the cutting of fiber optic cable in the Bay Area since July 2015. The FBI noted that there have been more than 12 in the region since January, and that it’s been hard to stop in part because there is so much critical cabling in the area and because cables are typically clearly marked, The Wall Street Journal reported. Authorities noted that these incidents show no sign of slowing down either, as they don’t have a clear suspect(s) or motive at this time. The Journal also noted that some instances of fiber optic-related downtime are not due to vandalism, but rather someone trying to steal metal.
fiber cut duct causes outageBy accident – This is perhaps one of the most common causes of fiber cuts, but nevertheless they are just as damaging. In one example a 75-year-old woman in the country of Georgia was digging in a field when she accidentally severed a fiber optic cable, in an article in The Guardian. As a result of the mishap, close to 90 percent of Armenia and parts of Azerbaijan and Georgia were completely without Internet for five plus hours.

Fire and Ice cause cable outage network downtimeBy force of nature – Tornadoes, hurricanes, earthquakes and other major natural disasters all have the potential to cut or entirely destroy fiber optic cabling. Other seemingly more benign forces of nature can also cripple connectivity, as Level 3 reported that 28 percent of all damages it sustained to its infrastructure in 2010 were caused by squirrels.

Calculating the impact of a fiber outage

trench digging causes fiber optic cut network outageIn some of these fiber cut outage incidents, the fallout can be relatively minor. A cut that occurs in the middle of the night on a redundant line can be easy enough to deal with, with service providers sometimes able to reroute traffic in the interim. Unfortunately however, such incidents often lead to much bigger problems for end users. For example, a cut fiber optic cable in northern Arizona in April caused many thousands of people and businesses to go about 15 hours with telephone and Internet service. This meant many shops had to either close or resort to manual tracking, and that personal Internet usage grinded to a halt, The Associated Press reported. More importantly, 911 emergency communications were disrupted in the incident.

It’s not just a hassle for end users, as cut fiber can severely impact public health when emergency services like police departments, fire stations and EMTs can’t take and receive calls. Plus, such incidents are very costly for service providers, forced to repair expensive infrastructure. They can also lead to canceled service, as customers become irate at service providers for failing to provide reliable connectivity at all times.

What’s a solution to fiber cut outages?

One easy way to avoid the problems related to cut fiber is to not have fiber at all and instead pursue a wireless dark fiber alternative. For example, after a cable snafu caused residents of Washington state’s San Juan Islands to go without telephone, Internet and cell service for 10 days in 2013, CenturyLink installed a wireless mobile backhaul option there, according to The AP.

By opting for a solution like a Gigabit Wireless Microwave, MMW, Free Space Optics or MIMO OFDM Radio, service providers gain a wireless alternative to cabling that is just as robust and fast as fiber. With the Gigabit Wireless link in place, cut fiber optic cabling is less disruptive to end users and ISPs.

Where do I found out more information on solving fiber Cut Issues?

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