As technology improves, however, and as the industry becomes more comfortable and familiar with 28 AWG cable, we’re starting to see it used in data center and enterprise network applications for many reasons:
- To reduce patch cord congestion
- To improve airflow around equipment
- To offer easier access to cables and equipment for maintenance purposes, with more space between cords
- To provide more room in cable trays – and lessen the weight placed into cable trays
- To allow sharper bend radii
- To achieve high-density layouts
As a result, earlier this year, TIA decided to establish a normative annex to ANSI/TIA-568.2-D that contains performance information about 28 AWG patch cords.
Generally, this standard requires conductor sizes of 22 AWG to 24 AWG in horizontal cables, and 24 AWG to 26 AWG in patch cord cables. But, TIA has recognized that, in certain cases, it may be necessary or desirable to use 28 AWG cable cords. Using 28 AWG will now be allowed as part of the standard – as long as ANSI/TIA-568.2-D requirements are followed.
A few of these important ANSI/TIA-568.2-D requirements are discussed in detail below...
DC Resistance
DC resistance – a measure of how difficult it is to pass a DC current through a conductor – shall be measured in accordance with ASTM D4566, which outlines standard test methods for electrical performance properties of cable insulation and jackets.
For all cable categories, the DC loop resistance of any structured cabling channel shall not exceed 25 Ω corrected to a temperature of 20 degrees C.
To make sure that your structured cabling channel will meet the DC loop resistance, it is recommended to keep the overall length of 28 AWG patch cords to a minimum (less than 15 m). Longer lengths are possible, but special attention to the overall DC loop resistance would be required.
Insertion Loss
It’s safe to assume that, in most cases, cable with a large OD has less insertion loss than a cable with a small OD (such as 28 AWG cable). Because insertion loss levels are higher in smaller-diameter patch cords, additional de-rating is necessary.
| Example of 28 AWG Patch Cord Usage | ||
|---|---|---|
| 28 AWG Patch Cord Length | Maximum Perm. Link Length | Resulting Channel Length |
| 6.2 m (20.2 ft) | 90 m (295.3 ft) | 96.2 m (315.5 ft) |
| 10 m (32.8 ft) | 82.5 m (270.7 ft) | 92.5 m (303.5 ft) |
| 15 m (49.2 ft) | 72.8 m (238.7 ft) | 87.8 m (287.9 ft) |
Cable insertion loss limits are determined by multiplying applicable horizontal cable insertion loss requirements by a de-rating factor of 1.95. This allows a 95% insertion-loss increase to account for smaller wire gauges and design differences.Because the de-rating factor for a 28 AWG patch cord is 95%, it’s 95% more “lossy” than a horizontal cable of the same length.
We’ll keep you updated as the appendix to ANSI/TIA-568.2-D is released so you’ll be one of the first to know when 28 AWG cable is officially included in the standards. Make sure to subscribe to our blog updates so you don’t miss it!
作者简介
Ron Tellas
Belden企业解决方案业务部高级解决方案架构师
Ron Tellas 是射频设计和电磁传播方面的主题专家，于 2016 年加入 Belden，帮助制定智能建筑技术和应用的路线图。 他现在利用这些经验将系统、设备和连接纳入网络解决方案。 Ron 代表 Belden 参加多个标准组织、国家电气规范委员会并担任 FMP 联盟的董事会成员。 他拥有电气工程硕士和学士学位、工商管理硕士学位，也是 17 项美国专利的发明人。 罗恩因其对电信行业的杰出和有影响力的贡献而自豪地荣获 2024 年 Harry J. Pfister 奖。