Deploy and Test Shielded Cable with Category 8
2016 年 9 月 22 日/一般
TIA TR-42.7 メタル配線分科委員会は最近、現在開発中の IEEE 25GBASE-T および 40GBASE-T のアプリケーションをサポートするための最新のツイストペア・カッパー・システム、カテゴリ 8 配線（TIA 568 C.2-1）の仕様を承認しました。
With all the buzz surrounding Category 8, you and your customers might be wondering how exactly it will impact the deployment and testing of cabling infrastructures.
Let's take a closer look at where it will be deployed and some of the key characteristics that impact installation and testing.
Data Center Only
Characterized to 2 GHz and specified for 30-meter, 2-connector channels, Category 8 is intended as a data center application--you won't likely find it in the LAN. これは、新しく登場する 25 Gb/s および 40 Gb/s の速度が存在するメタル配線によるサーバー間接続でデータセンター・エッジ・アプリケーションを対象としています。
While some high-speed direct attach SFP+ and QSFP+ cables can support these higher speeds in switch-to-server applications, those cables have short distance limitations of about 5 to 7 meters. Category 8 came about because its 30-meter distance capability is ideally suited for more flexible, manageable deployments where edge switches are placed at the end-of-row or middle-of-row locations. Since it shares that same connector and can autonegotiate with existing Ethernet technologies, it provides handy interoperability with those technologies.
Alien Crosstalk Remains
Category 8 cabling is a shielded cabling system. In other words, it uses shielded connectivity and FTP cable where the four twisted pairs are surrounded by a foil. Foil shielding is critical for preventing noise from entering or exiting the cable.
We already know that at higher frequencies, crosstalk between adjacent cables (i.e., alien crosstalk) is a much greater concern. That is why alien crosstalk became a requirement for Category 6A. At four times the 500 MHz frequency of Category 6A, Category 8 will of course continue to require compliance--along with all of the parameters you've been testing to for Category 6A.
Just like with Category 6A shielded cable, you should see hardly any alien crosstalk on a Category 8 system. But just like with Category 6A shielded, you will still need to test for it. その理由は?
First, Cat 8 has much more stringent alien crosstalk requirements. Second, shielded cabling can fail alien crosstalk testing if it's not installed correctly, such as the shield not being connected or clamping down on its non-conductive side.
Shield Integrity Will be Paramount
If you're not familiar with deploying and testing shielded cable, you will have to be with Category 8. That means installers and contractors will need to ensure prudent cable-connector shield termination and proper grounding and bonding measures
In a data center where a copper link is running from one grounded panel in a grounded rack to another grounded panel in a grounded rack, an open shield can still pass Wire Map. That is because shield continuity is historically a DC measurement that will reach the remote unit through the common building ground rather than through the cabling link. As a result, troubleshooting a link with an open shield will be extremely difficult.
Thankfully Fluke Networks already has the technology to address the issue. Only the DSX-5000 CableAnalyzer™ offers shield integrity testing using a patented AC measurement technique for preventing grounded racks in a data center showing that the shield is connected, even when it isn't.
You've Got Time
Now that the TIA Category 8 specifications, components and link limits are complete, work on the ANSI/TIA-1152-A field testing standard can be finalized. Fluke Networks is the project leader and editor for this standard, which defines the field test methodology and the Level 2G accuracy.
Besides, you've got plenty of time to get a handle on all the ins and outs of Category 8. There are no Category 8 components currently shipping, nor is there any 25GBASE-T/40GBASE-T equipment commercially available. In the meantime, Fluke Networks is working closely with leading cabling manufacturers to ensure simple, reliable testing of their solutions can be performed in the field when you start installing them.