Deploying Wireless Connectivity In Subterranean Worlds

By Ed Sullivan

Providing reliable voice and data communications that is flexible and durable enough for underground mining operations has been a labyrinth of issues until now. Advanced connection technology today makes it simple and economical to couple fiber optic networking with an integral power source for truly flexible wireless access.

Advanced and reliable network communications will be required by law in underground mines within the next few years, according to the Mine Improvement and New Emergency Response Act of 2006. The question is, will meeting this technological challenge result in consternation, disruptions and ongoing pricey investments – or will you use this occasion as an opportunity to improve both safety and productivity?

"Not later than 3 years after the date of enactment of the, a plan shall, to be approved, provide for post accident communication between underground and surface personnel via a wireless two-way medium, and provide for an electronic tracking system permitting surface personnel to determine the location of any persons trapped underground or set forth within the plan the reasons such provisions can not be adopted," states the Act.

"The underground mining industry could benefit in a huge way in what we take for granted with typical surface-based wireless communications technologies," says Will Gove, General Manager for Canadian Operations of Mine Site Technologies (MST). Headquartered in Sydney, Australia, MST is a global specialist in communications technologies for underground soft- and hard-rock mining applications.

Yet, like most above-ground applications, subterranean mining operations not only face a profusion of network communications issues, but also exceptional economic ones. There is the inherently harsh environment, the need to frequently relocate communications access points, and potential for soaring maintenance costs - in addition to the critical need of providing unbroken communications and tracking capabilities for mobile people and equipment.

"The mandate of the Act has energized MST to develop a wireless system that would fulfill that safety mandate and much more," Gove explains.

Partnering for a solution
To develop a far-reaching underground wireless solution, MST developed its ImPact Technology Suite, a network communications platform product line that extends a mine's Ethernet topology into the underground workings. While the product line includes both wired LAN and wireless LAN platforms, it is the wireless connectivity that promises to address many of the "infrastructure" and "data communication" challenges that are typical of subterranean mining environments.

The optimum solution would be hybrid connector-cable carrying both fiber-optic communications as well as power.

"Researching a provider of that technology led us to Applied Optical Systems (Plano, TX)" says Gove. "Applied Optical Systems (AOS) designs and manufactures fiber optic connectors and terminals for harsh and rugged environments."

While AOS products include "tactical" fiber optic connectors conforming to U.S. military specifications, MST was particularly interested in the "F-Link" series that includes versions designed for hybrid applications. Those are able to support port counts from 2 through 34 channels across 4 shell sizes of product.

"AOS were able to produce a connector that connects very easily to our ImPact system," Gove explains, "which enables us to put wireless access points anywhere needed throughout a underground installation."

MST began working with AOS to develop the specs including some unique features for a heavy-duty ("mine-hardened") version of the F-Link as an adjunct to the ImPact system. The outcome was a very robust product that provided mine operators with a very effective "plug & play" connector that allows for ease of installation with the mine.

The challenges to overcome
Gove's team knew that MST wanted to integrate a technology that would allow the ImPact System to carry two-way voice and data over a wireless network. Having many years of serving the mining industry, they also knew that mining environments were exceptionally challenging.

"In traditional wireless networking you need to power up every single device with 110-Volt AC power," Gove explains. "With our system and the F-Link Inter-connect System we are able to carry the power down the same cable that also carries voice and data. That means you only need to have power every fifth or sixth device. Also, the F-Link connector allows the composite fiber cable to be easily connected to other devices in the network with a "three turn twist action"

Gove adds that many mine operators deploy Category 5 (or 5e) twisted pair cable as the backbone in their networks, however, this cable can only be run in maximum lengths of 300 ft., whereas the ImPact/F-Link system can allow for cable runs of to 2 kilometers.

Also, the copper in Category 5 cable is problematic in underground mining because copper is subject to interference from magnetic forces created in the presence of many high-voltage lines, which can cause corrupt data and sporadic performance. The fiber optic solution has no such problems.

"The underground mining environment is very tough," Gove says. "It is usually either wet or dusty. Furthermore, you often have equipment running into or over cables and connectors. All of that spells ‘maintenance,' which you don't have with the F-Link. It's waterproof and dustproof and very durable. And it doesn't take a specialist to install it or move it, which could add up to major savings."

Complete connectivity
Gove says the F-Link makes the ImPact system highly adaptable for the mining environment.

Due to maximum flexibility of "provision independent channels", gender selectable plug or receptacles and total environmental sealing of connector system, the F-Link is ideal for almost any application including military, commercial and industrial applications.

"As long as the devices are 802.11-certified they are able to communicate through the network," he says. "That includes personal devices such as PDAs, laptops, VOIP devices and cell phones. Our users have complete flexibility to talk to each other, talk to mine operations on the surface, or make calls outside the system."

Gove adds that productivity is an anticipated byproduct of the wireless communication system's flexibility. The system allows for automated collection of data, for example. This can incorporate digital (paperless) forms on laptops or PDAs, so that when an equipment operator needs to submit a daily maintenance form, maintenance form, it can be quickly completed via electronic form on a PDA or laptop and then sent wirelessly to the central data collection for review and storage.

"The system adds a lot of communications power," he says. "That could also include sensor-based data such as temperature, humidity, airflow and gas, which can also be collected centrally."

F-Link, the first connector system to embrace the emerging trend toward hybrid (the combination of fiber optic and electrical power transmission), within the same cabling sheath, also offers a comprehensive family of back shells, assessors and shell sizes.

Applied Optical Systems designs, develops, and manufactures fiber optic solutions through the efficient application of passive fiber optic components, cabling, systems, and leading fiber optic technologies for the mobile and fixed, military, governmental and industrial markets.

SOURCE: Applied Optical Systems