The FOSC name has been synonymous with excellence in sealing, fiber management, ease of use, and design flexibility since the FOSC 100 closure was first introduced in 1986. FOSC closures have always been engineered specifically for fiber optic applications; they are not modified copper closures. The difference shows-ask someone who has worked with the product.

FOSC 400 closures combine proven fiber management hardware with a highly reliable sealing system. Base-to-dome seals on FOSC400 closures are mechanical for ease of installation and re-entry, and cable seals feature a unique Raychem heat-shrink sleeve and hot-melt adhesive system that is installed with a hot-air gun. Common materials, accessories, and practices are used throughout the product line to simplify training, reduce inventory, and enhance productivity.

FOSC 400 fiber optic splice closures are available in three sizes; the FOSC 400 A, FOSC 400 B, and FOSC 400 D. All sizes are designed for use with any cable construction (loose buffer tube, central core tube, loose fiber, and ribbon), in any environment (aerial, pedestal, buried, handhole, and manhole), and for numerous splice applications (express, tap-off, branch, and repair).
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Fiber Optic Splice Closures

FOSC 400 D5 Closure
Fiber Optic Splice Closures

FOSC 400 A4 Closure
Fiber Optic Splice Closures

FOSC 400 B2 Closure
Fiber Optic Splice Closures

FOSC 400 B4 Closure
Description N/A This is the largest of the FOSC 400 closures. It has one oval port, five large round ports and can terminate seven cables (or up to twelve cables with the use of branch-off clips). The splice capacity is 288 single mechanical, 576 single fusion, or 1728 mass fused fibers. The versatile slack basket can store ribbon fiber or expressed, uncut loose buffer tubes. N/A This is the smallest of the FOSC 400 closures. It is intended for low fiber count cable splices and “tap-off” splices. Tap-off splices are those where most of the fibers in a cable are “expressed” uncut through the closure and only a few fibers are cut and re-spliced to feed a building or Optical Network Unit (ONU). The FOSC 400 A4 closure comes ready to store expressed loose buffer tubes. An optional slack storage basket is available for express stranded fiber and ribbon fiber.

As with all FOSC 400 closures, the slack storage and splice capacity of the FOSC 400 A4 closure depends on a number of factors including cable construction, splice type, and slack fiber lengths. Refer to the Closure Capabilities chart that follows for more details. 		N/A These two closures are identical except for their end cable port configurations. In addition to a large oval port for the main distribution cable, the B2 closure has two large round ports for branch cable splices and the B4 closure has four small round ports for multiple drop applications.

The FOSC 400 cable sealing system provides a great deal of flexibility. For example, four small cables can be terminated in the two round ports of a B2 closure with the use of branch-off clips. It is also possible to terminate three cables in the oval port of either closure. 		N/A These two closures are identical except for their end cable port configurations. In addition to a large oval port for the main distribution cable, the B2 closure has two large round ports for branch cable splices and the B4 closure has four small round ports for multiple drop applications.

The FOSC 400 cable sealing system provides a great deal of flexibility. For example, four small cables can be terminated in the two round ports of a B2 closure with the use of branch-off clips. It is also possible to terminate three cables in the oval port of either closure.
Spliced Fiber Storage Capacity - Single Fusion N/A 576 N/A 32 N/A 96 N/A 96
Spliced Fiber Storage Capacity - Single Mechanical N/A 288 N/A 24 N/A 48 N/A 48
Mass Fusion N/A 1728 N/A 144 N/A 288 N/A 288
Slack Storage Capacity - Buffer Tubes N/A 18 N/A 8 N/A 8 N/A 8
Slack Storage Capacity - Stranded Fibers N/A 96+ N/A 96 N/A 96 N/A 96
Slack Storage Capacity - 12 Fiber Ribbons N/A 144 N/A 12 N/A 24 N/A 24
Port Size N/A N/A N/A Large Round Ports N/A Small Round Ports
No. of Ports N/A N/A N/A 2 N/A 4
Splice Capacity N/A 36 48 72 N/A 12 16 24 N/A 12 16 24 N/A 12 16 24
Cable Blocking Components N/A Blocking None
Valve for Flash Test N/A None Valve
External Grounding N/A Grounding None
Cable Seal Type N/A Tabular Wraparound
Cable Seal Port Type N/A Oval Round