Transcript Tech_2 Module 7 on F..

教程 FOR TECH 2
Effective Integration Requires Expertise….
Field Testing實地試驗
Tech 2 教程
教程 7: Field Testing 實地試驗
Isaac Yeo RCDD
Wire Map - is simply a check to see that wires are
connected one-to-one at each end.
布線規則是設置布線的各個規範(象使用層面、各組線寬、過孔間
距、布線的拓樸結構等部分規則,可通過...它們的設計結果叫做原
理圖（線路圖 ）
In a balanced twisted-pair cable, the test should
indicate:平衡[對稱]雙芯絞合電纜必須通過以下的實地測試：
• Continuity to the remote end. 遠端延續性
• Shorts between any two or more conductors. 導體互相短路測試
• Transposed pairs. 交叉線對
• Reversed pairs. 顛倒配對
• Split pairs. 分叉線對
• Shield continuity (e.g., only for shielded cabling).屏蔽延續性
• Grounded conductor. 接地線
WIRE MAP線路圖 Common wiring errors 會犯一般配线錯誤
Correct
正確
Cross or
Transposed pairs
交叉線對
Reversed pairs
顛倒配對
Split pairs
分叉線對
Wire Map線路圖 –
Troubleshooting recommendations for a balanced twisted-pair test
failure平衡[對稱]雙芯絞合電纜問題處理的建議
 Check terminations for correct color code.
 檢查顏色代碼是否正確
 Ensure that the equipment cords do not include a
crossover between two pairs.
 確保各配頭線不包含任何交叉線對
 In the event of a short or open, use TDR or length to
determine at which end the fault has occurred.
 在線路短路或斷開的情況下，就該使用TDR或直线刻度长
度來鑑定問題的所在
DC Loop Resistance 循環直流電阻
-This is the resistance of the wire pair when short-circuited at the far end.
-線對發生電阻情況當遠端發生短路
-This resistance can be very useful as a stand-alone diagnostic test to identify
a poor contact that may be causing an insertion loss failure.
-這電阻具有明顯用途當單獨診斷性試驗一診斷出因為線路不良接觸而產生
的所謂電信信號衰減的情況
-Is tested on coaxial cables and is measured between the center conductor and
shield of the coaxial cable.
-普遍實驗在同軸電纜上，試驗測試將在中心導線與屏蔽同軸電纜上之間．
DC Loop Resistance 循環直流電阻
The values will be different for each pair combination, due to the
different twist rates between the pairs.
各別線對的組合將產生不同測試數值，這是因為各別線對擁有各自的缠距
Looking at the above result, we could conclude that:從以上的測試數據，我們可結論：
a) the 1,2 pair has the tightest twist １，２配線對的密度缠距值是最大的
b) the 7,8 has the least twist. ７，８配線對是最低的缠距
Traveling Down the Copper Highway
往下移動的銅質總線
A
simple “model” to study and explain the
parameters
 以下的模擬圖解識參數
 Signals are like electrons following a
somewhat bumpy path
 電信訊息的電子粒行走的路徑是崎岖不平的
Propagation Delay 傳輸延遲時間- is a measurement of the time required for
a signal to travel from one end of the transmission path to the other end.
測量信號在傳輸線上終端器件是上升或下降所延遲的時間
Electrons travel at
constant speed
電子粒運行速率常數;
(max 555 ns納秒
later ..)
( 20 cm or 8” per ns,
1 ns = 0.000 000 0001 s
NVP * speed of light光速)
Propagation Delay傳輸延遲時間
 Is a measure of the time required for a signal to propagate from one
end of the circuit to the other
 測量信號在兩端的終端器之間傳輸線上所延遲的時間
 Propagation Delay is the principle reason for a length limitation in
LAN cabling
 傳輸延遲時間是限制局域網絡電纜線的長度為基本準則
 Most structured wiring standards expect a maximum horizontal
delay of 570 nanoseconds (nS)
 結構性配線標準大多數必須具備570納秒最大值的延遲時間
 Excessive propagation delay can have only one cause: the cable is
too long
 劇烈傳輸延遲時間的產生，恐怕只有一個理由：電線太長
遠端的輸入信號
負載端信號
Length 長度－ The length of a link may be estimated
from the electrical length measurement.
電子長度測試可讓你估計一條傳輸線的所需要的長度
Field testers measure the "electrical length" base on the round-trip
propagation delay of the link. This is the time required for an electrical pulse
to travel to the end of the link and back to the tester.
實地測試者可根據一個傳輸點利用電脈沖來測量信號在通過某個互連傳輸環境傳導
時引起的反射,如電路板軌迹、電纜、連接器等等。
This measurement technique is called Time Domain Reflectometry or TDR.
著種測量法叫做『時域反射計』．
To convert a time measurement into a distance (length) measurement, one
needs to know the speed with which the signal travels along the link.
所得的時間測量可轉向為所需知的長度
The NVP (Nominal Velocity of Propagation) expresses the speed with which
electrical signals travel in the cable relative to the speed of light in space or
vacuum.
電子是以近似恒定的速度運動，那就可將它與光速的比值定義爲一個常數，叫做額
定傳輸速度—NVP
If NVP is given as 0.69, meaning that electrons is traveling at 69% the speed
of light.
額定傳輸速度—NVP給予0.69測試數據，這表示電子用著69% 的光速運行
Length長度
When we measure the time required for a signal to travel the
length of the link and back, and we know the NVP of the cable, we
can calculate the electrical length of the link.
我們在長度測試中，用NVP乘以光速再乘以傳輸往返時間的一半，即傳
輸延遲就是電纜的實際長度。
Since the signal has traveled up and down the cable (twice the
length), the equation for length is:
Length = (NVP * Measured Time Delay * Speed of Light)/2
電子信號在傳輸線內是上下波動不停，那麼電纜的實際長度方程式是
長度 = (NVP *傳輸延遲時間* 光速)/2
The speed of light in space (or vacuum) is 300,000,000
meters/second or 0.3 meters/ nanosecond. (A nanosecond [ns] is
one billionth of a second.)光速是300,000,000 m/秒或 0.3 m/納秒．一
個納秒等于十億分之一秒．
 NVP for a Category 5 UTP cable is approximately 69% which
means that an electrical signal travels along a Category 5 cable at
approximately 0.2 m/nanosecond.
NVP在一條Category 5 UTP 的電纜上大約有69% ，這表示電子信號運
行在這條傳輸線上的時間是大約0.2 m/納秒．
A time domain reflectometer (TDR) method is used to
calculate the length of a cable by measuring the time it
Length長度
takes a pulse to travel down
the cable and back (round-trip
delay). This time is twice the propagation delay.
Time Domain Reflectometer 中文意思爲光時域反射儀。OTDR
是利用光線在光纖中傳輸時的瑞利散射和菲涅爾反射所産生的背
向散射而制成的精密的光電一體化儀表．
To calculate the length for balanced twisted-pair cable:
預算平衡[對稱]雙芯絞合電纜的實際長度：
電纜實際長度
真空光速
* Note注
If the incorrect NVP is entered into the tester the results can
be totally misleading where a 91 m link appears to pass the
test whereas the true reading may be a failing 105 m link.
如果把不正確NVP的信號輸入測量器，這會導致易誤解的訊息．
Length長度
In balanced twisted-pair cables, each pair may have a different twist
rate and sometimes different dielectric materials. This variation results
in a different propagation delay for each pair.
平衡[對稱]雙芯絞合電纜，每一配線對或許會有各自的缠距 ，不同的绝缘物
質．這表示各自配對的不同的傳輸延遲時間
If a field test instrument uses the same NVP for all pairs, the reported
length will be different for each pair.
如果實地測試儀器使用同樣的NVP來測試所有的線對上，得到的測試結果將
各所不同．
Standards require that the shortest electrical length be used as
the basis for the pass/fail decision (e.g., the shortest electrical delay
should be used to calculate the link length).
標準的要求則是最短的電氣長度當使用來辦別測試的獲得是否超越限度．（最
短的傳輸延遲可用在計算傳輸線的長度）
Therefore, a channel with four pair-lengths reported at 99, 100, 101,
and 103 meters would pass a 100 m maximum length specification.
因此，４條線對在一個頻道得到的測試成績是99, 100, 101, and 103
meters ．通過一個100 m為最大限度的標準測試．
Length長度-- Troubleshooting recommendations for a balanced
twisted-pair test failure
平衡[對稱]雙芯絞合電纜的問題處理建議
 Verify that the correct NVP has been set for the cable.
 確認測驗電纜的NVP是正確的
 Check to see if extra cable length is installed and that the patch
or equipment cords are not too long.
 檢查是否有安裝額外的電纜和確保接線或各種電源插頭線不太過長．
 Note that a channel is 100 m (328 ft) and a permanent link 90 m
(295 ft).
 確保測試頻道約100 m (328 ft) 和一條永久連接線是90 m (295 ft).
Delay Skew延遲偏差- is the differences in the propagation delay
between the fastest and slower pairs within the same cable sheath
UTP電纜中的各繞對由于纏繞數和每一繞隊的電特性的不同而導致各繞對的傳輸延遲稍有
差異，各繞對之間的延遲差異就是延遲偏差。的時間延遲
The length of every electronic road
in a cable is slightly different
because of twist rates
因為缠距，之所以每條電纜有各自不同繞
對之間的距離
A typical data cable:
(max 50 ns difference
..)最大限度５０納秒
分差
an electronic highway with four lanes
典型的電信傳輸電纜：一個擁有四條跑道的電子總線
Propagation Delay Skew傳輸延遲








Is the difference between the propagation delay on the fastest and slowest
pairs in a UTP cable.
UTP電纜中的最快與最慢線對限度差別的傳輸延遲時間
Skew is important because several high-speed networking technologies,
notably Gigabit Ethernet, use all four pairs in the cable.
延遲偏差對于以多線對電纜同時傳輸數據的高速並行數據傳輸網絡是一個非常重要的
參數
If the delay on one or more pairs is significantly different from any other, then
signals sent at the same time from one end of the cable may arrive at
significantly different times at the receiver.
如果繞對之間的延遲偏差過大，就會失去比特傳輸的同步性，接收到的數據就不能被
正確地重組
Well-constructed and properly installed structured cabling should have a skew
less than 50 nanoseconds (nSec) over a 100-meter link.
一條妥善安裝的結構化布線系統，它的延遲偏差在一條100-m電纜必須少過５０納秒
Insertion loss / Attenuation 插入损耗/衰耗
is represented by the
electrons that get stuck
電子粒被困住
Fewer electrons
show up!
極少的電子粒顯現
There are potholes in the road….
路徑布滿了障碍
heat!
heat!
Insertion loss / Attenuation 插入损耗/衰耗
Insertion loss is a measurement of the loss in signal
resulting from the insertion of a component, or link, or
channel, between a transmitter and receiver.
插入損耗是指發射機與接收機之間,插入電纜或元件産生的信號損耗,通
常指衰減。
Attenuation is where the signal is diminished due to losses
incurred throughout the transmission medium be it fibre or
copper.
衰減(Attenuation)：指信號沿鏈路傳輸的減弱。
 The smaller the loss in decibel (dB), the better the
performance.
越小分貝(dB)數質，其效能越強
Insertion loss / Attenuation 插入损耗/衰耗
 Electrical signals transmitted by a link lose some of their
energy as they travel along the link. The loss of signal strength
in the cable is attenuation
 在局域網中，當電纜超出規格中的最大長度時所出現的一種信號強度
損失現象。衰減會阻止成功的數據通信。
 The more attenuation you have, the less signal is present at the
receiver
 衰減越多，發送信號功率越差
 Attenuation increases with both frequency and length.
衰減增加電纜的載頻與長度
Possible causes for Attenuation failures 衰耗出現的原因
1)
2)
3)
4)
5)
Excessive length 長度過長
Poorly terminated connectors / plugs. Compare the
attenuation on the four pairs. If only one or two pairs has high
attenuation, this suggests an installation issue 拙劣地安裝電
纜連接器．
Impurities in the copper cable 銅線內含有的雜質
Wire Gauge. 24 gauge wires will have less attenuation than
the same length 26 gauge (thinner) wires. Also, stranded
cabling will have 20-50% more attenuation than solid copper
conductors 線規． 24線規比26線規（更細的線）產生更少的衰
耗．絞合接線法比固定銅導體高出20-50%衰耗現像
Temperature 四周溫度
Return Loss回程損耗- Return loss is a measurement of the power reflected
from the cabling 回波損耗是電纜鏈路由于阻抗不匹配所産生的反射,是一對線
自身的反射。
There are bumps in the road that cause some
electrons to bounce back
路徑布滿障礙物，這導致電子粒有反射
Return Loss
回程損耗
 Return Loss (RL) is a measure of all reflections that are
caused by the impedance mismatches at all locations along
the link
 是衡量整個信道部件是否阻抗匹配的指標
 In simple terms, it can be thought of as an echo that is
reflected back by impedance changes in the link.
 它可解釋為回音在交流電傳輸反射回來的電路的阻抗
 Any variation in impedance from the source results in some
returned signal
 從發射端已產生的電路的阻抗的信號同時也在回程信號內
 Expressed in decibel (dB)
 用(dB)表示
回程損耗
Return Loss
The ratio of the reflected voltage to the incident voltage is
used to determine the return loss.
反射電壓與入射的電壓的分差比率可以計算出回程損耗
反射電壓
所獲電壓
入射電壓
發送端
接收端
電阻的變化
The larger the value of return loss in dB, the better the
performance.
回程損耗的貝里dB數質越大, 越大其功效
Possible causes for Return Loss failures
導致回程損耗的原因
Variable patch cord impedance – change patch cord接插線
2)
產生隨機變量的電阻-更換接插線
3)
Patch cord impedance changes due to handling effects
4)
Installation practices拙劣的安裝法
5)
Non-compliant cable 不當的電纜
6)
Non-compliant connecting hardware 不當的連接硬體與配備
7)
Additional unnecessary untwist in terminations 多余搓合線對
Below show 2 terminations.Take note of the minimum jacket
removal and twists being maintained.
1)
Crosstalk 串擾
The road is not level and electrons fly off!
路徑不平穩, 導致電子粒掉隊
Near End Crosstalk Test (NEXT)
近端串擾實驗
“Stray” Electrons return back to the beginning on a
different pair『走失』的電子粒在近端的線對找回起點
Near End Crosstalk (NEXT)



近端串擾實驗
When a current flows through a wire, an electromagnetic field is created
which can interfere with signals on adjacent wires.
當電子粒開始在電線展旅程，電磁場將會產生
In LANs, NEXT occurs when a strong signal on one pair of wires is
picked up by an adjacent pair of wires
當LANs首次開始使用UTP系統作爲傳輸媒質，噪音限制了應用範圍，來源就
是外部的噪音幹擾和內部其它線對的幹擾。
NEXT loss is a measure of the signal coupling between any two pairs
along the entire length of the cabling. These combine as they reach the
receiver of the instrument at the near end.
該串擾是當設備在發送端傳輸的信號耦合到另一對線的相鄰接收端引起的．
近端
發送端
測試器
接收端
Near End Crosstalk (NEXT) 近端串擾實驗


As frequency increases, this effect becomes stronger.
频数的增加，影響力越強
Each pair is twisted because this allows opposing fields in the wire
pair to cancel each other. The tighter the twist, the more effective the
cancellation and the higher the data rate supported by the cable 每條
線對必須扭曲因為這可消除各自的電磁場．互相的扭曲綑綁越緊，消除
功效越大與及越高的數據傳輸率


If wires are not tightly twisted, the result is Near End Crosstalk
(NEXT)
如果電纜線不綑綁很緊，近端串擾將會產生
The larger the value
of NEXT loss in dB,
the better the
performance.
近端串擾數質越大，其功效越強
Possible causes for Near End Crosstalk failures
導致近端串擾實驗的原因
1)
2)
3)
4)
5)
6)
Poorly twisted terminations at connection points. All connections
should be twisted to within 13 mm of the point of termination
差的設計和低劣的布線所導致的
Poorly terminated connectors
/ plugs. Check the connections
at that end & replace /re-terminate
拙劣的安裝聯接器
Split pairs 分叉線對
Improper category of components is used.
使用不正確的配備
Female couplers used to joined cables
使用雌接口在連接電纜
An inappropriate test configuration being selected. Category 5e
installation to meet Category 6 performance
選擇不適當的測試設定
Far End Crosstalk Test (FEXT)
遠端串擾實驗
“Stray” Electrons continue to the far end on a different pair
『走失』的電子粒繼續運行在遠端的線對上
Far End Crosstalk Test (FEXT)

遠端串擾實驗
Far End Crosstalk is similar to Near End Cross Talk (NEXT), except
that the signal is sent from the local end and crosstalk is measured
at the far end.
遠端串擾跟近端串擾很相似，除了發射端傳輸信號訊息與串擾是在遠
端接受測試．
 Because of attenuation, signals that induce FEXT can be
much weaker, especially for longer cable lengths
因為衰耗的產生影響，信號訊息所引起的遠端串擾將會減弱，尤其長距離的
電纜最為顯著．
Attenuation
衰耗值
Far
End
遠端
Equal Level Far End Crosstalk (ELFEXT)
等電平遠端串擾


Equal level far-end crosstalk (ELFEXT) is the crosstalk measured on a
disturbed pair at the opposite end from which the disturbing signal is
transmitted, normalized by the attenuation contribution of the cable or
cabling.
是遠端串擾損耗與線路傳輸衰減的差值，以db爲單位。是信噪比的另一種方
式，即兩個以上的信號朝同一方向傳輸時的情況。
The larger the value of ELFEXT loss in dB, the better the performance.
等電平遠端串擾數值越大，功效越大接收端
近端
擾動信
號訊息
遠端
遠端串擾
發射端
接收端
衰耗值
The concept of “power sum”綜合近端串擾的理論
Power sum takes crosstalk from all 4 pairs into consideration. Remember it
can happen at both ends.
綜合近端串擾把四條線對的串擾列入考慮範圍．記得兩端同時發生這現象．
Power Sum Crosstalk(PSNEXT)
近端串音特性總和

Power sum crosstalk is used to specify a combination crosstalk.
近端串音特性總和乃定義不同對數之訊號傳輸所造成之影響
 In a 4-pair cable, power sum NEXT expresses the combined effect of the near-end
crosstalk from the three other pairs
綜合
近端串擾(Power sum) 一相鄰接收線對產生串擾的總和近端串擾, 其值為在4對雙絞線
的一側 ,3個發送信號的線對向另值。
 Power sum crosstalk is used as a requirement for applications that communicate over
multiple pairs at the same time.
綜合近端串擾的運用是一種規則要求，如綜合線對傳輸在同個時間上．
 Both NEXT and ELFEXT
can be specified as a
power sum since the
receive pair could have
simultaneous crosstalk
from the three other pairs.
NEXT近端串音特性總合值,與ELFEXT
等值遠程串音值，對綜合近端串擾
(Powersum)限值應符合，這因為3個
發送信號的線對向另一相鄰接收線對
産生串擾的總和近端串擾值。
Power Sum Crosstalk


近端串音特性總和
Both NEXT and ELFEXT can be specified as a power sum since the
receive pair could have simultaneous crosstalk from the three other
pairs.
近端串音特性總和乃定義不同對數之訊號傳輸所造成之影響,同時包括NEXT
近端串音及FEXT遠程串音
Power Sum Crosstalk is important as more and more applications use
all pairs within a jacket (e.g. Gigabit Ethernet).
近端串音特性總和很重要因為越來越多配備的電纜在使用多線對來傳輸信號，
符合未來網絡的需求具備全功率總和近端串音特性
Alien Crosstalk外來串擾(ANEXT)
-
-
-
-
Alien crosstalk (AXT) is electromagnetic noise that occur
in a cable that runs alongside one or more other signalcarrying cables.
外來串擾(aliencrosstalk)簡單講,就是相鄰線纜對被測線對的噪
音耦合
Occurs between different cables in a group or bundle,
rather than between individual wires or circuits within a
single cable.
它多在線纜捆綁、端口堆疊的情況下發
生。由于噪聲源于相鄰線纜,無法通過
受影響線路的電路抑制來取消。
Attenuation to Crosstalk Ratio (ACR)
衰減串擾比



Is the calculated difference in dB between attenuation and crosstalk
measurements for a balanced twisted-pair.
ACR它是電纜上的信号衰減和近端串擾之間的差值，用db 表示。
Due to the effects of attenuation, signals are at their weakest at the
receiver end of the link. But this is also where NEXT is the strongest.
Signals that survive attenuation must not get lost due to the effects of
NEXT.
因為衰減的影響，信號在接收端比較微弱．反而， NEXT近端串擾越強．那些信
号順利通過衰減后不在進一步损耗，因為NEXT近端串擾的強力牽制著．
ACR is an important figure of merit for twisted pair links.
ACR對于一個兩對線的應用是非常重要．随著高速網絡應用的出現，二對線傳
輸信号以不能滿足全雙工、高帶寬的傳輸要求，因此一些新的參數需要考慮在内，
以保證數據傳輸的順利進行。
Attenuation to Crosstalk Ratio (ACR)
衰減串擾比
It provides a measure of how much 'headroom' is available, or how much
stronger the signal is than the background noise.
測量電纜的淨空值（ headroom ），和信道信號與外來幹擾信号的差值
ACR differs from signal-to-noise ratio (SNR) because it excludes any
additional or external noise.
ACR是體現整個系統信号與串擾比SNR的唯一參數。SNR也考慮其它幹擾信号，是
網絡性能的決定性因素。
ACR also can be expressed as a power sum attenuation-to-crosstalk ratio
(PSACR), when a power sum crosstalk is used in the ACR calculation.
衰減串擾比（ACR）與綜合衰減串擾比（PSACR）測試. 衰減串擾比測試是將衰減
和近端串擾的測試結果進行數學比較（微分計算）。
The greater the ACR, the better.
ACR數值越大越好．
Noise Tests





幹擾能力測試
External noise can contribute to performance degradation on any
transmission system (with the exception of optical fiber).
外來的幹擾降低 裝置,設備或系統的工作性能與正常性能的非期望偏離.
Potential sources of noise are electromagnetic equipment and other
cabling.
幹擾來自强电磁幹擾或布線網
Noise testing after initial installation of the cabling may not detect
potential noise sources unless the facility is completely operational.
Even then, intermittent noise sources may not show up during testing.
幹擾能力測試在通過第一次的網絡測驗后，也許無法分辨幹擾潛在來源．除
非全自操縱系統中，間斷性幹擾來源將不會顯現在測驗中
Noise tests may be useful to troubleshoot problematic links or
channels.
幹擾能力測試可在電纜連接或頻道故障測試發揮用途
Time Domain Reflectometer時域反射器(TDR)




A time domain reflectometer (TDR) instrument sends pulses of energy
through the cabling under test.
時域反射器(TDR)是一個能夠發送信号通過一個網絡媒體到檢測電纜連續性和其
他屬性的設備。
When these pulses encounter the end of the cable, or cabling fault that
causes an impedance change, a portion of the pulse energy is reflected
back to the source.
在一根電纜上加載一系列電壓脈沖，在遇到大的阻抗變化時這些電壓脈沖會被反
射回測試儀。
Elapsed time to the returned pulse measures twice the distance to the
fault, and the shape of the returned pulse can identify the type of fault.
開路和斷路發射正電壓脈沖，短路反射負電壓脈沖。該測試儀還可以記錄被反射
脈沖的時間和極性，據此就可以
計算出電纜長度以及至斷點和短
路點的距離。
TDR is a powerful tool in
troubleshooting cabling
problems—primarily
return loss failures.
威力強大的測量儀器，
以電纜故障測試用途最廣
Balanced Twisted-Pair Cabling Acceptance Tests
平衡[對稱]雙芯絞合電纜可用性測試

i.
ii.
Two configurations are defined for field-testing horizontal balanced
twisted-pair cabling:平衡[對稱]雙芯絞合電纜實地測試具備以下兩個設備配置
Permanent link 永久鏈路
Channel link. 數字信道鏈路
Permanent Link


永久鏈路
All the permanently installed horizontal cable, the mated connection at
the wiring closet end of the link, the telecommunications outlet at the
far end of the link, and an optional transition point.
所有的永久鏈路安裝都運用在水平對絞電纜工程上，終端的電信出線口與選
擇性的轉移點
Maximum length is 90 meters.
網段距離最長是90米
接線板
Transition Point or
轉移点 Consolidation Point
永久鏈路（最長約90 meters）
Permanent Link (90 meters max)
电信出口
Channel Link



數字信道鏈路
Includes up to 90 meters of horizontal cable, a work area equipment cord,
an optional transition point, 2 cross-connections in the telecommunications
closet, a patch jumper between these two connections, and a
telecommunications closet equipment cord. In simple terms, the channel
includes everything necessary to get data from a PC in an office to a hub in
a wiring closet.
這包括了９０米的水平對絞電纜，工作區跳線，選擇性的轉移點，二層交叉
互連電信套間，一條在兩個連接點的跳線器和電信套間跳線．
Maximum length is 100 meter.
網段距離最長是100米
Test Limits試驗限值-- The test limits for balanced
twisted-pair cabling are:平衡雙芯絞合電纜測試限值
 Wire map requires correct continuity on all pairs.
線路圖需求所有的線對具備高度符合延續性
 Length is 90 m (295 ft) for the permanent link, and 100 m (328 ft) for
the channel. The pair with the shortest electrical delay is used for
the link length calculation that is to be compared to the maximum
length limit. Accurate measurement of length requires correct NVP
value. This can be obtained from the cable manufacturer or by
calibration .永久鏈路的網段距離最長是９０米，水平對絞電纜數字信道鏈路
的網段距離最長是100米．逐節信号傳送置距的可通過線對最短的電磁延遲計
算．準確的長度測量需求正確的NVP數置．這個從電纜承包商得到相關資
料．
 Insertion loss is the sum of the contribution from all the components:
Insertion loss of cabling = Sum in dB (e.g., insertion loss of
connections, cable, and cords). If the measured insertion loss is less
than 3 dB, do not use for pass/fail determination.

插入損耗是指發射機與接收機之間,插入電纜或元件産生的信号損耗,通常指衰
減。（插入損耗＝電纜，連接點，插件等的總數dB）如果插入損耗少於３
Db，禁止用在故障測定
Test Limits試驗限值-- The test limits for balanced
twisted-pair cabling are:平衡雙芯絞合電纜測試限值
 NEXT loss is the sum of the contribution of the cable and only nearend connectors—one or two for the permanent link, and two for the
channel. The connectors at the far end are not included, since their
contribution is considered negligible. NEXT loss must be tested from
both ends of the cabling link.
 ELFEXT is the sum of the contribution of the cable and
connectors—two or three for the permanent link, and four for the
channel. ELFEXT must be tested from both ends of the cabling.
 Propagation delay and delay skew assume the cable is the
dominant contributor and will vary based on length. The limits are
based on measurements equivalent to that made at 10 megahertz
(MHz).
Test Limits試驗限值-- The test limits for balanced
twisted-pair cabling are:平衡雙芯絞合電纜測試限值






Return loss is determined using a model that includes all the components of
the link. The limits are based on the category of components and cable lengths.
Return loss must be tested from both ends of the cabling link. If the measured
return loss reports less than 3 dB, it should not be used for pass/fail
determination. This rule is referred to as the “Return Loss 3 dB rule.”
回波損耗是電纜鏈路由于阻抗不匹配所産生的反射，是一對線自身的反射。回波損耗
（RL）的測試越發重要，因爲全雙工的網絡系統需要有合格的回波損耗的結果，以避
免發送信号端錯誤地識別回波信号爲有效信号。而實踐中發現正是這個參數的測試結
果給我們的測試人員帶來了太多的疑問，在此引一例來說明這個參數的一個不常見的
問題。在業界，這個問題我們通常也叫它3dB原則。
PSNEXT is obtained as a calculation from the pair-to-pair measured NEXT
values. It is the square root of the sum of the squared voltage contribution of
the different pair-to-pair crosstalk signals induced in the victim pair. PSNEXT
must be calculated from measurements taken from both ends of the cabling.
PSNEXT(綜合近端串擾):實際上是一個計算值,而不是直接的測量結果。PSNEXT 是在
每對線受到的單獨來自其他三對線的NEXT 影響的基礎上通過公式計算出來的。
PSELFEXT is actually a calculation, not a measurement. PSELEXT is derived
from an algebraic summation of individual ELFEXT effects on each pair by the
other three pairs. There are four PSELFEXT results for each end. Typically,
PSELFEXT results are about 3 db lower than the worst-case ELFEXT result at
each end of the link.
综合等效远端串扰不是測量而是一種計算法。等效遠端串擾是遠端串擾與衰減之間的
差,在進行遠端測試時,必然要考慮信号衰減因素的影響.等效遠端串擾在數值上排除了信
号衰減成分. 通常綜合近端串擾的數值比單獨的近端串擾的值要劣化2到3dB.
Instruments -儀器- 3 levels of instrument accuracy have been
defined for field-testing 三大實地測試驗儀器精確度的分級

Level IIe field test instruments are required for measurements up to
category 5e andClass D cabling.
第一分級：實地測試儀器提供category 5e andClass D 電纜線測試的需求．

Level III field test instruments are required for measurements up to category
6 and Class E cabling.
第二分級：實地測試儀器提供category 6 andClass E 電纜線測試需求．

An accuracy level IIIe has been defined and proposed for the
measurements of 10GBASE-T cabling up to 500 MHz to support the
deployment of 10 gigabit per second (Gb/s) Ethernet over balanced twistedpair cabling links.
第三分級：實地測試儀器提供10GBASE-T最大值為500 MHz，支持10
gigabit per second (Gb/s)以太網平衡雙絞線傳輸測試需求．
Digital Multimeter


數字萬用表
To measure voltage, current, and resistance in copper wire.
測量銅線內的電壓，電流和電阻
With the use of a shorting device
on one end of a pair of conductors,
continuity can be tested.
Inductive Amplifier and Tone Generator
電導放大器和音頻發生器

Provides the ability to identify a specific pair by generating a tone on
one end of a pair of conductors, with an inductive amplifier identifying
it at the opposite end.
對電纜施加1KHz音頻信号,配合電纜故障定點儀查找電纜路徑或對電纜低阻
故障進行定點,使電纜路徑查找及低阻故障定點．

Is primarily used for cable identification & troubleshooting.
主要使用在定位正确的電纜或故障判斷上．
Wire Map


線路圖實地測試器
Good for quick, basic tests for opens, shorts, crossed pairs, and miswires.
快捷，基本層的測試，通常運用在斷線，短路，交叉錯接線對等問題
LED Tester
Microtest Microscanner
Field Test Instrument
實地測試器
Fluke DTX 1800 Tester
Wire Map
線路圖實地測試器
Microtest OMNI scanner
Field Test Instrument
實地測試器
Agilent WireScope 350
Optical Fiber Cabling Tests -- Attenuation
 Attenuation is the decrease in magnitude of power
of a transmitted signal between two points,and is
used to express the loss of an optical system
measured in dB.
 The fiber type, link length, the number and quality of
terminations and splices, cable stresses, and
wavelength can all affect attenuation measurements.
 Attenuation measurements must be taken after
optical fiber cabling installation to ensure that the
attenuation is less than or equal to the allowed loss
budget.
Optical Fiber Cabling Tests光纜測試–
Optical bandwidth光纤带宽




Optical bandwidth is a measure of the information-carrying capacity of a
cabling system and is dependent on optical fiber quality and its fiber length.
Optical bandwidth varies inversely with system length.
A shorter length of optical fiber will have a greater bandwidth than that of a
longer length of optical fiber even when they have the same optical
bandwidth in MHz•km. For example, a 62.5/125 μm fiber with a 200
MHz•km bandwidth at the 850 nanometers (nm) window will produce a
bandwidth capacity in the order of 1 GHz at 90 m (295 ft).
NOTES: Because optical bandwidth cannot be adversely affected by
installation, optical fiber bandwidth field-testing is not performed.
Optical Fiber Cabling Tests光纜測試– Length長度

Length is measured to ensure the link does not exceed applicationbased requirements.
測量長度是避免光纜尺寸不匹配的情况發生

Length may be measured via propagation delay by using the optical
fiber’s index of refraction (IOR).
長度也許使用折射率(IOR)準則與传输时延一同測試．
Optical Fiber Cabling Tests光纜測試– Polarity－光纜極性

Polarity can be verified with an optical loss test set (OLTS) while performing
attenuation tests or by using a visible light source (e.g., a visual fault locator
[VFL]).
進行等級1測試時,要使用光纜損耗測試設備(OLTS)測量每條光纜鏈路的衰減,
通過光學測量或借助電纜護套標記計算出光纜長度,使用OLTS或可視故障定
位器(VFL)驗證光纜極性
 The VFL is a compact but
powerful visible laser source
designed to verify polarity, & also to help identify some causes of signal loss
(e.g., breaks, bends, faulty connectors, or splices) by emitting a bright beam
of red light into a fiber, allowing the user to see a break as a glowing or
blinking red light
這些模塊比其他的光纜測試方案更方便,包含更多的功能,包括雙光纜、雙波長
的測試與診斷,還集成可視故障定位器(VFL)。
 It is also used to check end-to-end continuity, identification of connectors in
patch panels or telecommunications outlets/connectors, and identifying
optical fibers during splicing operations.
内置的可視故障定位器（VFL）可查找光纜，驗證連通性和極性，並能發現
斷點
Optical Fiber Cabling Tests-- Visual Fault Locator
光纜測試－－光纜認證和測試
Optical Fiber Cabling Tests – OTDR
光纜測試－－光通讯测试仪表


An optical time domain reflectometer (OTDR) is used to characterize power
reflected along optical fibers with a graphical signature on a display screen.由
OTDR的測試原理可知，它是按一定的周期向被測光纖發送光脈沖，再按一定的
速率將來自光纖的背向散射信号抽樣、量化、編碼後，存儲並顯示出來。
The OTDR has the capability to measure the length of the optical fiber and
characterize the power loss between any two points along the optical fiber.
光通讯测试仪表(OTDR) 不但可以提供光缆的故障诊断，也可以計算光缆的長度，
功率損耗等诊断．
OTDR (Optical Time Domain Reflectometer)
光通讯测试仪表
OTDR (Optical Time Domain Reflectometer)
光通讯测试仪表
It is useful for:
實際的好處：
1)
I.
II.
III.
2)
Cable acceptance testing —The OTDR characterizes the quality of the cable,
either on the reel or installed, including:
電纜測試規範－ OTDR對電纜本身的質量和施工工藝以及光纜連接等方面
Measuring normalized optical fiber loss at the operating wavelength in dB/km.
測量光纖功率損耗
Detecting point faults or discontinuities. 尋找故障點
Measuring the cable’s overall length. 測量電纜／光纖的總長度
Documentation—Printed copies of OTDR traces provide proof of a system’s
integrity and performance. A trace of the entire length of optical fiber (e.g.,
commonly called a signature trace) is an extremely useful document for customer
cable acceptance, maintenance, and system upgrades because it is the as-built
point-to-point (PTP) optical fiber blueprint. These traces can be used to evaluate
consistency of insertion loss for connections along the optical fiber link and to
mitigate high loss events.
具備完善的紀錄功能，進行文檔備案，生成光纜鏈路全面測試報告
OTDR (Optical Time Domain Reflectometer)
光通讯测试仪表
3)
Troubleshooting and fault location —The OTDR identifies and locates
faults or breaks. Optical fiber discontinuities and localized losses in the
cable are easily visible on the OTDR trace display and can be compared
with original as-built trace records. In the event a high link loss is
measured using an OLTS, an OTDR can be used to identify high loss
events such as an individual connector or splice.
问题處理＆故障定位－ OTDR可測試與尋找故障定位．光纖缺陷與插入損
耗和光纜長度測量．OTDR 分析和光纜連接頭端接面潔淨度檢查集成在一
台儀器中，提供更高級的光纜認證和故障診斷。随機附帶的軟件可以管理
所有的測試數據，對它們進行文檔備案、生成測試報告。另外一方從以往
的數據可以比較現在的紀錄．
OLTS is Optical Loss Test Set
光損耗測試儀
Optical Fiber Cabling Tests
光纖測試

Premises optical fiber links should be tested bi-directionally & at their
two corresponding wavelengths:
光學纖維應當具備雙航向與以下２種相對應的波長
a) multimode（多狀態）at 850 nm and 1300 nm
b) singlemode （单模 ）at 1310 nm and 1550 nm).
 Link attenuation is calculated as: 連接衰減計算方程序：
Link attenuation連接衰減 = Cable attenuation電纜衰減+ connector
attenuation連接器衰減+ splice attenuation接續盒衰減
Cable attenuation (dB) = Attenuation coefficient (dB/km) x length (km)
Connector attenuation (dB) = Number of connector pairs (N) x connector loss
(dB)
= N x 0.75 dB
= 1.5 dB
Splice attenuation (dB) = Number of splices (S) x splice loss (dB)
= S x 0.3 dB
3 Basic segments of Optical Fiber Cabling
光纖測試三大基本部份


I.
II.
III.


Telecommunications cabling in premises environments is divided into
three basic segments:
電信網絡系統分成以下三大基本部份：
Campus (interbuilding) backbone 建築群骨架網
Building (intrabuilding) backbone 單建築骨架網
Horizontal and centralized cabling 水平布線與中央集匯布線網絡
Each of these segments differs from the others in average cable length
and number of cable runs. Because of these differences, testing
recommendations for each segment are different.
每一個部份跟以往其他平均的電纜使用，需求不同．因為之所不同，每個
部份的測試也所不同．
The three basic cabling segments, their cable characteristics, and testing
recommendations are shown in Table 11.3 of BICSI TDMM ver 11.
這三基本部份，有各自的電纜特質，測試方式
3 Basic segments of Optical Fiber Cabling
光纖測試三大基本部份
Guidelines to promote efficient and accurate testing:
提高效率與準確測試知道方針：
 Test jumpers should be factory-assembled, factory-polished, and be the same
optical fiber core size as the cabling system (e.g., 62.5/125 ìm jumpers for a
62.5/125 ìm system).
測試跳線必須經過工廠專業監察，裝配，與單芯光导向器的直徑相同．
 The power meter and the light source must be set to the same wavelength.
電子電度表與光源必須設定同樣的波長
 The power meter must be calibrated and traceable to the National Institute of
Standards and Technologies (NIST) or the applicable equivalent.
電子電度表必須調整為(NIST)國際標準
 The light source or OTDR must operate within the range of 850 ± 30 nm or 1300
± 20 nm for multimode testing.
雙模式測試的光源或OTDR 的操作在850 ± 30 nm or 1300 ± 20 nm之間．
 The light source or OTDR must operate within the range of 1310 ± 10 nm or 1550
± 20 nm for singlemode testing.
单模式測試的光源或OTDR 的操作在1310 ± 10 nm or 1550 ± 20 nm 之間．
 All system connectors, adapters, and jumpers must be cleaned before
measurements are taken.
在測試未進行之前,所有的連接頭, 適配器和跳線必須清洗乾淨.
問題與答案時間．．．
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