Cisco Cisco 10 Gigabit Modules 白皮書
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The se t w o me a su r e me nt s r e p e a t e d o v e r a l l st a t e s o f t he f i b e r ( p o l a r i za t i o n st a t e s o r p o si t i o ns o f t he f i b e r sha k e r )
a nd e nsu r i ng t ha t t he ma x i mu m TWD P i s w i t hi n t he L R M r e c e i v e r sp e c a nd t ha t t he E M B W me e t s t he mi ni mu m
sp e c i f i e d f i b e r b a nd w i d t h i n t he L R M st a nd a r d w i l l g i v e c ha r a c t e r i za t i o n o f t he l i nk .
a nd e nsu r i ng t ha t t he ma x i mu m TWD P i s w i t hi n t he L R M r e c e i v e r sp e c a nd t ha t t he E M B W me e t s t he mi ni mu m
sp e c i f i e d f i b e r b a nd w i d t h i n t he L R M st a nd a r d w i l l g i v e c ha r a c t e r i za t i o n o f t he l i nk .
2. To c o nt i nu o u sl y sw e e p t hr o u g h t he f i b e r st a t e s w hi l e t e st i ng t r a nsmi ssi o n t o a v e r a g e o v e r a l l f i b e r st a t e s.
Thi s me t ho d e nsu r e s t ha t “ r e a l i st i c l i nk s” a r e d e f i ne d ( me a ni ng a f i b e r t ha t i s w i t hi n 99% o f t he i nst a l l e d F D D I -
g r a d e , O M 1, O M 2 a nd O M 3 f i b e r s a t 220 me t e r s) a nd b y a v e r a g i ng o v e r mu l t i p l e f i b e r st a t e s, g r e a t l y i nc r e a se s
t he r e p e a t a b i l i t y o f o v e r -f i b e r t e st i ng f o r mu l t i mo d e f i b e r s.
g r a d e , O M 1, O M 2 a nd O M 3 f i b e r s a t 220 me t e r s) a nd b y a v e r a g i ng o v e r mu l t i p l e f i b e r st a t e s, g r e a t l y i nc r e a se s
t he r e p e a t a b i l i t y o f o v e r -f i b e r t e st i ng f o r mu l t i mo d e f i b e r s.
The o v e r -f i b e r TWD P i s t he n c a l c u l a t e d u si ng t he M a t l a b a l g o r i t hm d e f i ne d i n p a r a g r a p h 68.6.6.2 o f t he I E E E
L R M st a nd a r d a nd se t t i ng f i b e r st r e sso r s t o 0 , 1, 0 , 0 . I f t hi s p e na l t y e x c e e d s t ha t g i v e n i n t he st a nd a r d ( f o r t hi s
e x p e r i me nt w e u se d 4.2 d B , w hi c h i s t he ma x i mu m p e na l t y g i v e n f o r t he p o st -c u r so r st r e sso r ), t he n t he f i b e r i s no t
r e p r e se nt a t i v e o f a “ r e a l ” f i b e r o ne mi g ht r e a so na b l y e x p e c t t o f i nd i n t he f i e l d . The e f f e c t i v e mo d a l b a nd w i d t h
( E M B W) i s t he n a l so c a l c u l a t e d f r o m t he sa me w a v e f o r m, d e -c o nv o l v i ng t he b a nd w i d t h o f t he t r a nsmi t t e r a nd
r e c e i v e r u se d f o r t he me a su r e me nt . The
L R M st a nd a r d a nd se t t i ng f i b e r st r e sso r s t o 0 , 1, 0 , 0 . I f t hi s p e na l t y e x c e e d s t ha t g i v e n i n t he st a nd a r d ( f o r t hi s
e x p e r i me nt w e u se d 4.2 d B , w hi c h i s t he ma x i mu m p e na l t y g i v e n f o r t he p o st -c u r so r st r e sso r ), t he n t he f i b e r i s no t
r e p r e se nt a t i v e o f a “ r e a l ” f i b e r o ne mi g ht r e a so na b l y e x p e c t t o f i nd i n t he f i e l d . The e f f e c t i v e mo d a l b a nd w i d t h
( E M B W) i s t he n a l so c a l c u l a t e d f r o m t he sa me w a v e f o r m, d e -c o nv o l v i ng t he b a nd w i d t h o f t he t r a nsmi t t e r a nd
r e c e i v e r u se d f o r t he me a su r e me nt . The
I E E E S t d . 80 2.3a q
TM
-20 0 6
L R M st a nd a r d sp e c i f i e s i n t a b l e 68-2 a
mi ni mu m mo d a l b a nd w i d t h o f 50 0 M H z* k m f o r F D D I -g r a d e , O M 1, O M 2, a nd O M 3 f i b e r s; t hi s c o r r e sp o nd s t o a
mi ni mu m E M B W o f 2.3 G H z o v e r 220 m.
mi ni mu m E M B W o f 2.3 G H z o v e r 220 m.
The n t he p o l a r i za t i o n c o nt r o l l e r i s st e p p e d t o a no t he r p o l a r i za t i o n st a t e , a ne w w a v e f o r m i s c a p t u r e d , a nd t he
TWD P a nd E M B W a r e me a su r e d a g a i n. Thi s c o nt i nu e s u nt i l se v e r a l f i b e r st a t e s ha v e b e e n c a p t u r e d .
TWD P a nd E M B W a r e me a su r e d a g a i n. Thi s c o nt i nu e s u nt i l se v e r a l f i b e r st a t e s ha v e b e e n c a p t u r e d .
F o r e a c h t r a nsmi t t e r / f i b e r c o mb i na t i o n TWD P a nd E M B W a r e me a su r e d f o r e a c h o f se v e r a l p o l a r i za t i o n se t t i ng s.
The se me a su r e me nt s a r e p l o t t e d i n F i g u r e 4. L o o k i ng a t t he f i g u r e , w e c a n t he n sa y t ha t i f a l l TWD P / E M B W
v a l u e s f o r a ny p o l a r i za t i o n st a t e l i e w i t hi n t he g r e e n r e g i o n ( TWD P l e ss t ha n t he 4.2 d B d e f i ne d a t t he r e c e i v e r
e nd o f t he l i nk i n t he I E E E st a nd a r d , a nd E M B W g r e a t e r t ha n t he 50 0 M H z-k m d e f i ne d i n t he I E E E st a nd a r d ), t he
f i b e r u nd e r t e st i s a r e a l i st i c c a se l i nk f o r 10 G B AS E -L R M a p p l i c a t i o n a nd r e p r e se nt a t i v e o f t he w o r st r e a l l i nk o n
w hi c h a n L R M -c o mp l i a nt t r a nsmi t t e r a nd r e c e i v e r i s e x p e c t e d t o o p e r a t e . C o nv e r se l y , i f so me o f t he p o i nt s l i e
o u t si d e t he r e c t a ng u l a r a r e a , t he f i b e r i s no t p a r t o f t he 99% o f t he i nst a l l e d mu l t i mo d e f i b e r b a se a t 220 m w hi c h
t he I E E E d e f i ne d f o r 10 G B AS E -L R M .
The se me a su r e me nt s a r e p l o t t e d i n F i g u r e 4. L o o k i ng a t t he f i g u r e , w e c a n t he n sa y t ha t i f a l l TWD P / E M B W
v a l u e s f o r a ny p o l a r i za t i o n st a t e l i e w i t hi n t he g r e e n r e g i o n ( TWD P l e ss t ha n t he 4.2 d B d e f i ne d a t t he r e c e i v e r
e nd o f t he l i nk i n t he I E E E st a nd a r d , a nd E M B W g r e a t e r t ha n t he 50 0 M H z-k m d e f i ne d i n t he I E E E st a nd a r d ), t he
f i b e r u nd e r t e st i s a r e a l i st i c c a se l i nk f o r 10 G B AS E -L R M a p p l i c a t i o n a nd r e p r e se nt a t i v e o f t he w o r st r e a l l i nk o n
w hi c h a n L R M -c o mp l i a nt t r a nsmi t t e r a nd r e c e i v e r i s e x p e c t e d t o o p e r a t e . C o nv e r se l y , i f so me o f t he p o i nt s l i e
o u t si d e t he r e c t a ng u l a r a r e a , t he f i b e r i s no t p a r t o f t he 99% o f t he i nst a l l e d mu l t i mo d e f i b e r b a se a t 220 m w hi c h
t he I E E E d e f i ne d f o r 10 G B AS E -L R M .
Whe n f u l l st e p -b y -st e p c ha r a c t e r i za t i o n me a su r e me nt s ha v e t a k e n o v e r f i b e r , t he p o l a r i za t i o n c o nt r o l l e r o r f i b e r
sha k e r i s t he n se t t o c o nt i nu o u sl y sw e e p t hr o u g h a l l o f t he f i b e r st a t e s, a nd t he r e q u i r e me nt i s t ha t t he o p t i c a l
t r a nsc e i v e r i s a b l e t o f u nc t i o n e r r o r -f r e e o v e r a l l st a t e s o f t he f i b e r , i nc l u d i ng t he w o r st c a se TWD P a nd E M B W
p o i nt s o f t he f i b e r .
sha k e r i s t he n se t t o c o nt i nu o u sl y sw e e p t hr o u g h a l l o f t he f i b e r st a t e s, a nd t he r e q u i r e me nt i s t ha t t he o p t i c a l
t r a nsc e i v e r i s a b l e t o f u nc t i o n e r r o r -f r e e o v e r a l l st a t e s o f t he f i b e r , i nc l u d i ng t he w o r st c a se TWD P a nd E M B W
p o i nt s o f t he f i b e r .