Optical Transmission Network Node

Optical Transmission Network Node
1.ما يسمي SFD وبه 40wave length ...ويستخدم في FOADM
SFD means static filter dwdm
2.ده شيلف WDM ومعاه اتنين SFD
Type Alcatel
1830Pss "shelf name"
لكن شيلفات WDMالتي تعمل ROADM لا يتم تركيب SFDمعها

Foadm : fixed optical add drop mulitiplexer
Roadm: reconfigurable optical add-drop multiplexer

نستطيع ان نقول ان
FOADM
مثل pdh قديما ....حيث انه اذا كان لدينا تلاته نود
3nodes(A,B and C)
واردنا عمل طول موجي من Aالي C
ففي FADM يجب ان نذهب الي  B لعمل

back to back (B/B)
حيث انها يعمل Add/dropلكل الاطوال الموجيه في كل النود ....

اما ROADM
مثل Sdh ....
عندما نريد عمل
Wavelength Cross connection
فذلك عن طريق s\w mangement ولا حاجه لنا لعمل . B\B

FOADM VS ROADM
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FOADM, only a certain set of wavelengths are added or dropped at a OADM site. This creates several problems:

- If the wavelength you want to access is expressed (ie *not* one of the ones that is A/D'd) based on the fixed scheme, then you must change the fixed scheme (which is usually a disruprtive replacement of a fixed-filter system).

- If you really wished that a specific wavelength be expressed (i.e. not A/D'd) at a FOADM site, and that wavelength was part of the fixed A/D, then you would be forced to either re-generate that wavelength at that site or change the fixed filters

- The fixed filters usually A/D 4, 8, 16 specific wavelengths, which for any given network, would limit the topological flexibility. For example, what if I wanted 5 wavelengths to be A/D at a given site? Or, what if I wanted 4, but they were not the four that the fixed A/D was configured for?

ROADMs get rid of these limitations.

Tunable transceivers add another degree of flexibility in that you only need one tranceiver in order to service any given wavelength (within its tunable range).

Some OADM architectures are neither Fixed nor Reconfigurable. Instead, they are "broadcast & select". In this design, all wavelengths are expressed (but can be blocked) and A/D'd at the same time. In this case, again, you could either have tunable or non-tunable transceivers.