Fiber Optic Splice Closures (FOSCs) provide the
opportunity for three types of fiber optic splicing:
aerial, at grade or below grade. The advantages, in both
cost and functionality, of aerial splicing are discussed
in this article. Although a sealed FOSC is an option
for aerial splicing, a weather-tight breathable FOSC is
the most beneficial in this type of fiber installation. A
weather-tight FOSC creates the optimum environment
for safely and effectively housing fiber optic splices in
aerial applications. It is designed to protect from all
undesirable conditions, whether they may be harsh
temperatures, unwanted moisture or humidity. It is
also more advantageous than a sealed FOSC when
considering initial material cost, installation cost and
time, routine repair and maintenance cost, ease of
expansion and product training. An aerial, weathertight
FOSC is proven to be a sound and economical
method for outside plant fiber deployment.
When considering distribution of information on fiber optic cable in a Fiber Optic Splice Closure (FOSC), three types of splicing should be considered including above ground aerial, at grade or below grade fiber optic splicing. Each of these splicing types has benefits as well as cost and risk associated with deployment. This article defines considerations for slack loop aerial fiber optic splicing in risk, cost and reward. These comparisons will be limited to backbone and branch distribution in FOSC.
OUTSIDE PLANT CONSIDERATIONS
Three types of FOSC should be considered with aerial
splicing used in two broad applications:
Traditional slack loop cable splicing is the most common deployment. A coil of fiber optic cable is placed and the FOSC will be installed by another crew. This allows the cable to be opened and spliced to branch cables or cable ends. This type of splicing can utilize either a sealed FOSC or a weather-tight breathable FOSC for all splicing.
Taut sheath or no slack splicing occurs when there is a repair to a fiber optic cable damaged on the strand or when a no slack branch or drop cable is to be installed. This type of splicing can only be accomplished with an inline FOSC and typically occurs after plant design and deployment. This is a cost effective solution for repair or additional branch drops.
DRIVING FACTORS IN FOSC SELECTION FOR SLACK LOOP SPLICING
When defining what type of FOSC will best suit the deployment and maintenance expectations of a provider, consider these factors.
• Initial cost of goods – material needed to install and maintain the plant
• Initial cost of installation – labor cost for first pass placement and splicing
• Deferred cost of installation – material and labor costs in a “build as you grow” design
• Routine maintenance and repair – material and labor associated with environmental and accidental damage associated with outside plant fiber optic cable deployment
• Ease of expansion – material and labor cost associated with expansion (internal or external geographic expansion)
• Choosing the right material
- Proven and supported product
- Meets applicable industry standards
- Material availability and warehousing considerations
- Training time for current staff, contractors and future training
Many manufacturers provide FOSC in both sealed and weather-tight varieties. Consider the following:
• The cost of a weather-tight FOSC is typically less than a sealed FOSC.
• No special tools are required for installing a weather-tight FOSC.
• Initial training and new hire training times are reduced with weather-tight FOSCs.
• Sealed FOSCs typically have more associated kits.
• Sealed FOSCs are a universal product that can be used in any splicing location.
• Weather-tight FOSCs are limited to aerial strand locations.
The variable costs associated with the different types of Aerial FOSCs are highlighted below:
INITIAL FIRST PASS LABOR
The majority of this cost is labor spent on constants that remain stable between both types of FOSCs. The cable placement and coil lengths are constant. The setup and splicing at each location is constant on the first pass as sealed and weather-tight FOSCs can both be spliced at grade level. However, there is an opportunity to decrease time spent in low to mid-count splicing by splicing on the strand in a weather-tight FOSC. This is not possible in a sealed FOSC. Current fusion splicers are designed to withstand the weather in an outside plant deployment where strand aerial splicing can be a consistent time and cost saving methodology. This should be an area of risk versus reward depending on weather and technician proficiency.
The study below can be used two ways:
1. At-grade splicing can occur on both sealed and weather-tight FOSCs.
2. Aerial splicing can occur only in weather-tight FOSCs.
Aerial splicing in a slack loop-type design does not require special equipment to perform at the bucket. Considerations of environmental protection such as tents and heaters can improve productivity but are not required to perform the splicing. As mentioned above, taut sheath no slack splicing will require specific strand mount bracketry for the fusion splicer.
BUILD AS YOU GROW
Build as you grow is applicable in a phased build where branch cables are deployed after an initial backbone build and implemented as service is needed in a specific region. This time savings listed below would be applicable for each branch added to an existing coil left on the backbone cable. Sealed FOSCs must utilize at grade splicing to add a branch to the backbone. Weather-tight FOSCs can be spliced at grade or on strand.
The cost savings of utilizing weather-tight aerial FOSCs is one that can be realized for the life of the plant. There are many times when a FOSC needs to be opened other than splicing. From an OTDR to a red light fiber verification, a weather-tight aerial FOSC will save money. A typical trouble call can result in multiple FOSC openings to troubleshoot and repair an outage. The aerial option can be accomplished in half the time potentially performing the maintenance from a ladder eliminating the need for a costly bucket truck roll out.
TRAINING AND CRAFT PREPARATION
Typically, a weather-tight FOSC is not as complicated to install as a sealed FOSC installation. A weather-tight FOSC is designed to be more tolerant of field and craft variations during installation as it contains fewer parts and is less complex. Training craft personnel or contractors is significantly less than a sealed FOSC. The weather-tight FOSC installation does not need to be sealed to prevent the Telcordia-specified 20 feet of water out for seven days. Typically special tools are not needed and often use fewer tools than a sealed FOSC.
What are the benefits of aerial splicing for you and
your company? The benefits of time and cost savings
are clearly defined above, but what are the other
considerations in adopting this technology? The
aerial weather-tight (breathable) FOSCs have a 20+
year proven field record with products from multiple
vendors. The deployment of this technology has
spanned all of North and Central America with proven
protection in the harshest of environments from the
cold of Northern Canada to the heat in Mexico. These
have been approved and deployed in all markets and
fiber plant designs from RBOC to ITEC and CATV
providers. From an RBOC perspective, breathable
closures are recognized as Telephony grade solutions
verified in GR-771 for free-breathing FOSC.
The benefits and cost savings continue as your fiber plant matures with decreased maintenance cost due to ease of field troubleshooting and plant repair or expansion utilizing weather-tight FOSC. By design the weather-tight FOSC allows for ambient temperature and ambient humidity inside the FOSC as well as outside the FOSC. This prevents condensation from forming inside the weather-tight FOSC which ultimately would be sealed in the traditional FOSC. In areas where freezing is a concern, this closure is proven to have additional value. If condensation, moisture or rain were to migrate into a sealed FOSC the accumulation of frozen water can result in attenuation or total failure of optical links in the field. This cannot occur with a vented closure and fiber routing design in a weathertight FOSC. The design of a weather-tight FOSCs prevent water from ever being able to accumulate and reach the fiber cable or splice sleeve, preventing an attenuation or degradation that can occur from bare fiber being submerged in water for extended periods of time.
Rich Megill is the application engineering manager for AFL’s Optical Connectivity and Apparatus (OCA) division. With more than 30 years of experience in fiber optic technology, Rich started his career with Keptel, a division of ARRIS, where he designed network interface systems and fiber optic cable management products for telco residential and commercial applications.