OCAM7 Flashcards
What is WDM?
Wavelength Division Multiplexing allows for the transport of multiple data streams, each on a different wavelength, on a single fibre
What is DWDM?
Dense WDM - a physical transport technology with dense referring to the closing spacing between wavelengths. DWDM is based on 194THz as the centre frequency, which corresponds to 1550nm (the C-band). There can be unto 100+ wavelengths in a DWDM system and with amplification can span distances up to 1000s of Kms
What is CWDM?
Coarse wave Division Multiplexing - supports up to 18 widely spaced channels at 20nm. Is much less expensive that DWDM as doesn’t require complicated filters and the laser tolerances are less strict. However, can only cover spans of 80km and so not supported in OC transport networks
What is a client card?
An optical interface unit that interfaces customer protocol and customer bit rate over customer-side wavelengths. Client cards will interface the client wavelength onto a DWDM network
Bit rate can range from 100mps-100Gbps
What is a line card?
An optical interface unit with ports for transmitting and recovering signals. Line cards face the DWDM network and have fixed or a flexed protocol and bit rate. Some cards may support a specific wavelength or be tunable.. Other cards ay also have client-side optics known as transponder cards.
Bit rate can range from 1-400Gbps
What are the characteristics of a card?
1) Protocol and bit rate support for the client signal
2) DWDM wavelength supported for the card
3) Distance supported by the transmitter on the card
4) Ability to support wavelength selectivity
What is a band?
A subset of wavelengths, grouped together to take advantage of the fixed filters to support bulk add/drop multiplexing
What is a network element?
A network element or chassis are defined by the requirements of the particular network where they are located and their placement on that network. Their function is defined by the cards they contain. NEs are connected to create an optical transport network
What are the minimum components of a NE?
1) Card cage and or chassis
2) Power supply or input
3) Fans
4) Visual alarm and power indicators
5) Management interface card
6) Client and/or network facing cards (line)
What defines where DWDM network components are placed?
1) Adding or dropping customer signals at desired locations
2) The required number of customer channels
3) The physical distance between two sites
4) Operating over the existing fibre plant between provider sites
5) Future growth requirements
6) Ease of manageability
These components may be serrate drives or combined onto one card
What do DWDM components include?
1) Line cards
2) fliters to add/drop or pass through wavelengths
3) Fibre plant
4) Amplifiers
What is an optical filter?
Optical filters allow for the multiplexing of wavelengths onto a single fibre, allowing for capacity gains. However, the also add optical loss and are power limited.
The pass through traffic of a filter is a band rather than a single channel
What is a fixed filter?
An add/drop module that supports a subset of wavelength grid for flexibility and cost savings. This filter type is passive so no electrical power is needed. They are deployed in pairs to facilitate channels near-end add/drop to far-end add/drop. They pass through all incoming traffic that is not dropped locally.
What is an OMX?
Optical Module is a fixed filter consisting of multiple optical filters packaged together that adds/drops only the wavelengths that the individual filter is tuned to add/drop
Properties of Bragg Grating fixed filter
Bragg gating is an optical component packaged in an optical filter containing:
1) One band add and one band drop filter
2) One channel multiplex and one channel demultiplex filter
Hundreds of gratings are fixed to a specific range of ITU wavelengths.
Supporting wavelength range must match DWDM line optics
Each Grating reflects back some of the specified wavelength and allows the other to pass through
Cheaper filters add more loss and use more real estate
