optical interfaces lab last update 2014.01.21 1.0.0 copyright 2014 kenneth m. chipps ph.d. 1

Optical InterfacesLab

Last Update 2014.01.21

1.0.0

Copyright 2014 Kenneth M. Chipps Ph.D. www.chipps.com

1

Objectives of This Section

• Learn– How to configure optical interfaces

Copyright 2014 Kenneth M. Chipps Ph.D. www.chipps.com 2

Activating Optical Interfaces

• In this lab we will activate two types of optical interfaces– A fiber optic cable Ethernet interface such as

would be used to connect two nearby buildings to each other using singlemode or multimode fiber optic cable

– A fiber optic cable ATM interface such as would be used to connect two distant buildings to each other over dark fiber


Activating Optical Interfaces

• We will do the Ethernet interface lab in Packet Tracer

• The ATM interface lab will be done using Cisco 3640 routers


Fiber Optic CAN Link

• In Packet Tracer create this network



• Use the 2811 for the two routers• Place the NM-1FE-FX module in the

2811s in the larger left side slot– Connect the fiber ports using the orange fiber

optic cable link• Use the 2950-24 switches• Use the generic host


NM-1FE-FX Module

• The fiber optic module used in this case is the NM-1FE-FX

• It looks like this


NM-1FE-FX Module


NM-1FE-FX Module

• It fits in the router and connects to the fiber, either simplex or duplex, this way


NM-1FE-FX Module


NM-1FE-FX

• In general a FX module uses a 1300 nm near-infrared light source on two strands of optical fiber

• One for receive and one for transmit• The maximum distance is two kilometers

using multi-mode fiber optic fiber



• In the real world a link such as this would connect buildings like this

• Any of these four buildings could be connected



• Here are the commands to make this work


Building on the Left

– enable– config t– hostname BuildingLeft– int fa0/0– ip address 192.168.1.1 255.255.255.0– no shutdown– int fa1/0– ip address 192.168.2.1 255.255.255.0– no shutdown


Building on the Left

– exit– ip route 192.168.3.0 255.255.255.0 fa1/0– end


Building on the Right

– enable– config t– hostname BuildingRight– int fa0/0– ip address 192.168.3.1 255.255.255.0– no shutdown– int fa1/0– ip address 192.168.2.2 255.255.255.0– no shutdown


Building on the Right

– exit– ip route 192.168.1.0 255.255.255.0 fa1/0– end



• A connection over such a short distance as between any of these buildings should just work if everything is installed properly

• To be sure a power budget as discussed for the MAN link just below here can be computed first


Fiber Optic MAN Link

• Let’s switch to the MAN link using the Cisco 3640 routers with an ATM OC-3 module installed

• For a link like this a singlemode fiber optic cable is used, which should make a connection up to 27 miles

• For example, we could connect the Irving campus to the Richardson location using a dark fiber link from this company




Irving Location Richardson Location


• At 23 miles the distance should be just within the maximum

• To be sure we will compute a power budget for the link

• With a power budget we are predicting that light reaching the receiver will be strong enough to be read correctly

• Here are the values for the interface card type that would be used for this link



• Let’s do a power budget for the proposed link

• If we use the Intermediate Reach card the power budget is 13 dB

• If we use the Long Reach card the power budget is 29 dB



• Here is a discussion on this from the Cisco Network Modules Hardware Installation Guide section on ATM cards

• The power budget - PB - is the difference between transmitter power - PT - and receiver sensitivity - PR

• For the Intermediate Reach card the values are– TX -15 dB and RX -28 dB



– The available power budget being 13 dB– Computed in this way

• PB = PT – PR• PB = –15 dB – (–23 dB)• PB = 13 dB


Link Loss

• Power loss - Link Loss - over a fiber-optic link arises from the following– Passive components

• Attenuation caused by cables, cable splices, and connectors is common to both multimode and single-mode transmission

– Chromatic dispersion• The signal spreads in time because of the differing

speeds of the different wavelengths of light


Link Loss

– Modal dispersion• In multimode fiber, the signal spreads over time

because of the different propagation modes

– Higher-order mode loss• This loss results from light radiated into the fiber

cladding

– Clock recovery at the receiver• This recovery consumes a small amount of power


Link Loss

• The power lost over the data link is the sum of all these losses

• This table gives an estimate of the amount of loss attributable to each cause


Link Loss


Power Margin

• The difference between the power budget and the link loss is the power margin - PM

• If the power margin is zero or positive, the link should work

• If it is negative, the signal may not arrive with enough power to operate the receiver


Power Margin

• For example– In this case where single-mode fiber optic

cable is being used as there is a single transmission path within the fiber modal dispersion does not occur


Power Margin

– Here is the example they provide of this type of calculation• The power budget is the output power, in this case

20 Bb, minus the loss due to the attenuation of the single over distance and the connectors in the path

• Two buildings 8 kilometers apart• Connections through a patch panel in an

intervening building with a total of 12 connectors


Power Margin

• PM = PB – LL– = 20 dB – (8 km x (0.5 dB/km) – 12 x (0.5 dB))– = 20 minus (4 plus 6)– =20 minus 10– = 10 dB

– A positive value means this link should have enough power for transmission

– The PM in this case is 10– The link will work as specified



• How about our link• Will it work• First the Intermediate Reach module• The distance is 23 miles or 37 km• PM = 13 – ((37*0,5)+(12*0.5)• PM = 13 – (18.5 + 6.0)• PM = 13 – 24.5• PM = minus 11.5



• That will not work• How about the Long Reach version• PM = 29 – ((37*0,5)+(12*0.5)• PM = 29 – (18.5 + 6.0)• PM = 29 – 24.5• PM = 4.5• We must use the Long Reach version of

the cardCopyright 2014 Kenneth M. Chipps Ph.D. www.chipps.com 38


• Since we know it will work, let’s configure the equipment

• It is best to test in a lab before deploying equipment into the field

• So we will connect the two routes back to back



• For the back to back connection we will use a multimode patch cable

• First, we need to clean and inspect all of the connectors, patch cable, and the router interfaces

• Next let’s enter the configuration for each router

• First the Irving router



• enable• config t• hostname Irving• interface atm 3/0 • atm clock internal • interface atm3/0.1 point-to-point • ip address 10.0.0.1 255.0.0.0 • pvc 1/5



• encapsulation aal5snap • protocol ip 10.0.0.2 broadcast• end



• Now the Richardson router



• enable• config t• hostname Richardson• interface atm 3/0• interface atm3/0.1 point-to-point • ip address 10.0.0.2 255.0.0.0 • pvc 1/5



• encapsulation aal5snap • end



• Test the link by pinging between the routers from each end


optical interfaces lab last update 2014.01.21 1.0.0 copyright 2014 kenneth m. chipps ph.d. 1

Documents

link copyright

fiber optic module

dark fiber copyright

shutdown copyright

fefx module copyright

routers copyright

optical interfaces copyright

network copyright