It's a round, round world

Loose tube MDP vs. flat ribbon in the data center

The cable world is round. It's a fact that round cables are easier to bend, install and are more durable than oval or even flat cables. This holds true, particularly in data centers (DC), which is a microcosm of a LAN, WAN and MAN structured cabling environments. Encapsulated in one location, but containing many subsystems, data centers commonly contain many different cable types, both copper and fiber, depending on the applications and distance requirements between the many defined spaces. However, in an environment where best installation practices and concern for scalability, space and cooling are critical, data center consultants and designers are selecting small diameter round cables.

 
Whereas copper best fits into horizontal distribution, this article focuses on the backbone and fiber optic cables which offer inherent bandwidth capabilities for future applications in this space.
 
Flexible choices
According to industry standards for data centers (TIA-942), when selecting cable, focus on these attributes:
·         Flexibility with respect to existing services
·         Useful life of the cable with respect to scalability
·         Facility size
·         Channel capacity and
·         Vendor recommendations
Additional considerations for cable selection need to address issues such as higher mechanical robustness, improved cooling efficiency, fire loading, as well as flexibility and modularity for easy moves, adds, and changes.
 
There are three main fiber optic cable construction choices installed in data centers -- ribbon, loose tube, or tight buffer. Where ribbon cables were designed as a high-density configuration, these are actually quite bulky when high-fiber counts are needed as multiple ribbons are stacked and become difficult to bend and route. Because of the stacked matrix make-up, the cable has an inherent preferential bend, which means it will bend in one preferred axis. If twisted or pulled in the opposite direction of this axis, the fibers could become attenuated.
 
Tight-buffered cables allow the fibers to move independently. But since each fiber has its own 900 um buffer, the diameter of the cable can become very large at higher strand counts. And with the onset of 40/100 Gb Ethernet coming soon, the number of fibers required will increase dramatically.
 
The best alternative is a loose tube cable, which allows the fibers to lie freely within buffered tubes inside the jacket. Since the fibers are loose and not bonded in a ribbon matrix, they do not exhibit any preferential bend and can be flexed in any direction with significantly reduced risk of damage relative to the ribbon cables.
 
 
Keeping it Cool
In data centers, it is imperative to maintain a cool temperature (68°-77°F, according to the TIA-942) to assure reliability and to eliminate network outage due to any possible active equipment overheating. The deployment of high-density blade servers (also getting smaller by design) and storage devices to handle the demands of increasing data traffic and back-up has resulted in higher rates of power consumption and heat generation. In addition, cables in pathways (above the equipment and below the floor) can also inhibit airflow and, as a result, can compromise cooling efforts.
 
Size matters
Another critical concern for data center managers is efficient space utilization. With the increasing bandwidth demands mandated from fixed square-footage footprints, the cabling infrastructure needs to be as small as possible while maintaining sufficient capacity to address expected growth.
 
Berk-Tek’s micro data center plenum (MDP) cable, designed as the smallest diameter fiber optic cable, conforms specifically to the indoor-only DC and building backbone environment. This new MDP cable design incorporates Berk-Tek’s new patent-pending construction to provide a 50% smaller cross sectional area than equivalent fiber count indoor cables.
 
In data center applications, the MDP cables help alleviate cabinet and pathway congestion, considerably enhancing airflow, facilitating more efficient cooling.    When compared to traditional ribbon interconnect, premises distribution, and indoor/outdoor loose tube cables, this new breed of cables offers improved density and ease of installation especially when paired with pre-terminated assemblies, for both the DC/SAN space, as well as intra-building backbone infrastructure.
 
The significantly reduced tube diameter provides the opportunity have “ribbon-like” length control with the low-stress environment of a loose tube cable. The size advantages of the more traditional loose tube cables are more significant for MDP cables. The greatly reduced diameter can lead to a significant reduction in pathway size, see Table 1. The smaller diameter also makes it easier to route within the cable management racks and patch panels.
 
MDP to Ribbon Dimensional Comparison
MDP vs Ribbon
 
 
 
 
 
Scalability
Data centers are ever-expanding and evolving as new applications are added, particularly in shared co-locations. Clearly, the ease of installation and ease of termination yields significant advantages to the installers when time is of the essence for new construction, or expanding an existing data center or simply handling  routing moves, adds and changes.
 
Deploying a fiber-based backbone in data centers for today and tomorrow’s needs now comes with options. When designing your data center, explore the options and take a look at the small diameter MDP cables to provide the best solution for installation advantages today and scalability for tomorrow, adding up to the best long-term return on investment.

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Your Contact

Carol Oliver Berk-Tek Marketing Analyst
carol.oliver@nexans.com