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Tag Archive: dark fiber

1. Using Dark Fiber Optic Cables to Detect Earthquakes

   February 13, 2019 4:14 pm Leave a Comment

   Researchers hope to use networks of unused, dark fiber optic cables to help detect underground sound waves that can warn of an impending earthquake.

   Millions of miles of unused, dark fiber optic cables are installed underground. A research team of scientists from the University of California (Berkeley) and Lawrence Berkeley National Lab have been experimenting with a new predictive technique. This method may gather measurements of movement in the Earth’s crust that are superior to those obtained by current seismic detection systems.  

                                                                                                                                                                                                                                                                         Measuring Activity

   In seismology, scientists often have only a small number of sensors to use in detecting earthquakes. This is one reason why measuring vibrations through the Earth’s surface is an uneven, “touch-and-go” venture. Also, some seismically-active areas have many sensors on hand, while places distant from shifting tectonic plates may have very few. This variation in equipment can make it tough to measure seismic vibrations in places where, for example, fracking triggers earthquakes. Using the new method, users could turn each fiber optic cable length of a few feet into an individual seismic sensor.

   In this new experiment, the research team “borrowed” from other groups who have developed distributed acoustic sensing (DAS) methods. In DAS, laser pulses are used to detect minute vibrations along optical fiber/cable. Researchers insert units called interrogators along the optical fiber/cable. These interrogator units send out and sense short infrared laser pulses. Triggered by seismic activity, tiny strains on the optical fibers cause some of the laser light to be reflected and then bounced back to the sensor. By sending rapid pulses, the scientists can detect changes in the light scattering over time. By knowing the speed of light, they can pinpoint where the activity occurred.

   “Real World” Testing   

   With this latest technique, the researchers essentially tested the DAS method in the real world. They plugged their interrogators into the fiber optic cable line along the Department of Energy’s Dark Fiber Testbed. This 13,000-mile stretch of telecommunications fiber in the western U.S. is used for testing new communications equipment. The researchers targeted a 17-mile cable segment near West Sacramento, California, and recorded data from July 28, 2017, up to January 18, 2018.

   The research team successfully recorded information on the speed of sound waves traveling through the Earth. In fact, during September 2017, they detected and measured the massive 8.1 magnitude earthquake in Mexico (the strongest quake to hit Mexico in a century).

   Unfortunately, this detection technique isn’t ready to be used beyond research. But keep an eye open for possible use in the future!

2. Lighting Up Dark Fiber

   January 7, 2019 8:11 pm Leave a Comment

   

   Last month, internet speeds in Jackson, Mississippi, jumped from 1 Gb to 100 Gb. This leap forward is part of the city’s work to light up “dark fiber” in the robust fiber optic network that it owns.

   The Origin of Dark Fiber

   The term “dark fiber” refers to unused or underused fiber optic infrastructure (optical fibers, fiber cables and repeaters). Because it’s expensive to deploy cable (especially under oceans), companies typically install more fiber than they will need. This fact was especially true during the dot.com boom of the 1990s. However, after the bust of the early 2000s, many companies either went bankrupt or merged. The result is that today, in addition to “lit fibers” (fibers currently transmitting data by light), there are many “dark fibers” (unused fibers) within the same networks.

   
   

   Cities Lighting UpBecause it’s possible to buy or lease these fibers, some cities and companies see using dark fiber as an appealing way to save money or create a new revenue stream. However, there are other factors to consider because using dark fiber isn’t straightforward. Buying and managing a fiber network takes skills that many organizations simply don’t have. Also, when a group starts selling network bandwidth, it takes on the role of becoming an ISP.

   And on top of this, success isn’t always guaranteed. Take the example of California’s Santa Monica CityNet. In 2014, CityNet became the first 100 gigabit municipal network in the country. However, in its efforts to lease dark fiber, CityNet has signed up less than 2 percent of the business market since 2006. It has also collected only about $2.1 million in revenue over that time.

   Other Uses

   At least for now, dark fiber still has staying power. One factor driving its use is cloud computing which requires greater bandwidth. However, dark fiber could face greater competition as cities get “smarter” and 5G wireless communications roll out.

   Ironically, dark fiber’s strength may come through uses besides connectivity. At the Lawrence Berkeley National Laboratory, Dr. Jonathan Ajo-Franklin is using dark fiber to measure seismic signals. Dr. Ajo-Franklin’s team gained permission to access a section of a dark fiber network between Sacramento and Calusa, California. During a seven-month experiment, the team collected about 300 terabytes of data. Ultimately, they found that the same dark fiber installed for communications was also useful in making distributed measurements. These measurements included seismic wave fields, temperature, strain and vibrations that can affect infrastructure (such as the number of cars on a road). In other words, an unused fiber installed for a telecom network might also be used in sensing.

   What’s more, by using dark fiber, the team saved a substantial amount of money by replacing a critical, huge array of thousands of individual point sensors with an existing, installed fiber optic cable.