Fiber Optic Networks

If all systems are down, check the main power source. If that checks out OK then begin troubleshooting using the process of elimination.  Proceed as follows: Begin with transmitters and receivers – Use a power meter to measure the optical power being received at the receiver. If that tests out OK, you know that the problem is likely the receiver. If no light is being received by the receiver, ensure that the  transmitter has power. Check for breaks or severe bends in the fiber. Do this only after ensuring that the transmitter and receiver are OK.  A fault finder and OTDR are useful tools at this stage of testing. Hint: Begin checking fiber where people have the most contact with it, such  as patch panels, under desks, etc.

Wireless Office Networks
If experiencing problems while connecting a PC or other wireless host to the office network:

1. Check all physical connections
2. Ensure that the wireless adapter in connected and configured properly
3. Ensure that the LAN port is active on the router
4. Check the IP address of the wireless adapter
5. Verify reachability using a “ping” command
6. Check that firewall protection is disabled on the host
7. Router and adapter should have the same settings for SSID, channel, wireless mode and security.
8. To locate a parameter mismatch for security, temporarily disable security for both the router and adapter.
9. Debug and resolve any issues regarding current protocols, including possible mismatches with Extensible Authentication Protocol  (EAP).
10. Check for sources of RF interference

Various companies are offering alternatives to the smart grid for controlling energy consumption by appliances. For example, RLtec manufactures appliances that use Dynamic Demand Management (DDM) technology. These appliances sense energy fluctuations in the
grid and adjust their electrical consumption accordingly.

DDM appliances don’t offer the comprehensive solutions of the smart grid. On the other hand, they don’t need to communicate with the utility company for instructions. That means they can react very quickly to changes in the grid. Some people suggest that these self-regulating devices do a better job of conserving energy, so there is no need to relinquish control of appliances to the smart grid.

Niche Market

DDM appliances will likely find a niche within smart grid homes. This is particularly true for large appliances if DDM’s faster response time can be shown to produce more savings than similar appliances that are controlled by the grid.

A happy compromise may be to have these appliances monitored by the grid, but left to operate on their own under normal circumstances.

“Phasors” can enable the smartgrid to make stunningly fast power adjustments. Phasor Measurement Units (PMUs) are high speed sensors that can be distributed throughout the nationwide smart grid and monitored by global positioning system (GPS) satellites.

A phasor represents the shape of an alternate current waveform. Ideally, a waveform would have the same desired shape throughout the
smart grid. The clock pulses from GPS satellites can take precise time measurements to reveal sections of the grid where the waveform shapes have changed, which indicates that power quality has degraded. This real-time reporting would enable the automated smart grid to take immediate corrective action.

The HAN zone is connected to the Nan zone. The NAN zone is connected to the WAN zone. Like the old Fats Waller song, connectivity is the key when it comes to the smart grid. Every “zone” (area network) within the smart grid is interconnected to form a cohesive hole.

Home Area Network (HAN)
Within the home HAN connects appliances, computers, and other electrical devices to the Smart Meter, an emergency monitor is also the home’s principal Smart Grid energy interface.

Neighborhood Area Network (NAN)
Outside the home, the Smart Meter connects to other Smart Meters within the NAN, typically as a “mesh” network.

Wide Area Network (WAN)
NAN interfaces with the WAN, which integrates local networks with the smart grid on the national level.

During a recession, end users may be more inclined to upgrade their existing networks rather than install a new infrastructure. Network upgrades can be very simple or very complex, depending on the type of upgrade projects you take on.

Here are some useful things to keep in mind as you perform a network upgrade:

• Many IT managers perceive that switching from copper to fiber must be done all at once. Explain that it can be done in stages, as budgets allow, using media converters.
• When possible, choose “auto-negotiation” media converters that will automatically negotiate speed and compatibility.
• When looking for system bottlenecks in a legacy system, good places to begin are those areas where many cections converge at servers or routers.
• Sometimes an existing infrastructure has adequate speed and capacity but there aren’t enough ports to connect new users or equipment. A simple upgrade is to replace existing Ethernet wall outlets with 4-port Fast Ethernet switched outlets.
• PC’s in older legacy systems may negate some of the performance improvements of an upgraded system. Ask your client to consider new computers as part of the upgrade.
• Rule of thumb – Increasing network bandwidth also increases speed. A network that is running Ethernet 10-Mbps will operate 10 times faster when upgraded to Fast Ethernet (100 Mbps).

Overview:

• In a DWDM System, multiple wavelengths are transmitted down a single fiber. Dense Wavelength Division Multiplexing (DWDM) allows higher data rates and increased bandwidth to be transmitted over existing networks.
• The wavelengths are transmitted along the fiber in tightly spaced intervals. Due to Chromatic Dispersion, these tightly spaced signals will spread out as they travel down the fiber. They can spread out to the point that they blend into each other, causing errors in the transmission.
• Optical Spectrum Analyzers (OSA) can separate and display the multiple wavelengths combined on a DWDM system and create a graph of Power vs. Wavelength. Analysis can be performed on each individual wavelength within the signal. The power and bandwidth of each wavelength can be measured as well as its interaction with other wavelengths.
• OSA testing is performed during installation, commissioning and maintenance.

Certification:

• Verify transmission integrity over distance
• Determine where signal regeneration is required in an
optical network
• Uses PC software for documentation/certification reporting

Recommended Equipment:

Anritsu CMA 5000A OSA Analyzer
EXFO FTB-5240B OSA Analyzer

Bit Error Rate Testing (BERT)

Overview:

• A Bit Error Rate Tester measures the performance of a communication system. Bit Error Rate testing involves sending simulated data through a communication system and comparing the input data to the output data.

• Bit Error Rate is the percentage of bits that have an error compared to the total number of bits received. The Bit Error Rate (BER) represents how often a data packet has to be re-transmitted due to errors.

• A high Bit Error Rate increases the number of re-transmissions. This in turn increases the amount of time needed to send data through the system, slowing transmission speeds.

Troubleshooting & Certification:

• Measure network performance – verify number of re-transmissions

• Use test data to determine optimal data rate for the communication system

• Bit Error Rate Testing is used to determine the sources of Bit Errors in a system and to re-verify the BER after actions have been taken to remedy the issues.

• Uses PC software for documentation and certification reporting

Recommended Equipment

Anritsu MP1800 Signal Quality Analyzer

Overview:

• Polarization – Light consists of two perpendicular waves.  When light is sent down a fiber these waves travel two different paths (Polarization Modes).
• Due to imperfections in the fiber from manufacturing and stresses applied to the fiber during installation, the light in each path travels at different speeds. PMD creates a slow and a fast axis, which causes the pulse to distort or broaden. This broadening of the pulse causes interference at the receiver which limits the networks signal quality, its ability to transmit at higher speeds, and causes signal blending making it difficult for the receiver to interpret.
• Polarization Mode Dispersion increases with fiber link distance and bit rate, making it a critical factor in upgrading to 40 gig and 100 gig systems.

Certification:

• Measure Polarization Mode Dispersion to help verify performance of an installed fiber span. Determine if the span is qualified to be upgraded to transmit at higher bit rates.
• Since PMD is not constant and varies over time due to stress and environmental changes, PMD can be tested periodically to re-verify the PMD value of an installed fiber link. (Example: A fiber installed along a railroad track will exhibit a different PMD value when the train is running than on those days when there is no train).
• Uses PC software for documentation and certification
reporting.

Recommended Equipment:

Anritsu CMA 5000A PMD Analyzer
EXFO FTB-5500B PMD Analyzer

Overview:

• Measure the length and overall loss of an optical fiber
• Provide the location and loss value of any event along a fiber
• Create a graphical display of the fiber under test
• Certify and troubleshoot optical networks during Construction,
Maintenance and Restoration
• Has the ability to measure Optical Return Loss (ORL)

Certification:

• Verify integrity of cable reels prior to installation
• Measure splice loss during construction – verify splice meets specs.
• Measure End to End loss to certify fiber span meets loss budget
• Verify connector reflectance meets spec.
• PC Emulation Software – Generate Certification Reports
• Certify that Optical Return Loss (ORL) meets specs.

Troubleshooting:

• Fault Location – Locate a break in the fiber
• Detect Macrobends
• Pinpoint high loss splice events
• Locate highly reflective connections
• Compare traces to detect changes that
occur in a fiber system over time

Recommended Equipment:

FIS Deluxe Mini OTDR
FIS Advanced Mini OTDR
Anritsu MT9083A
EXFO FTB-150

Testing Procedure Overview:

• Minimal Equipment needed ( Power Meter & Light Source)
• Measure End-to-End loss of an optical fiber
• Some Units:
• Have the ability to measure Optical Return Loss (ORL)
• Have user adjustable Pass / Fail Thresholds – quickly verify if a span is within specs.
• Are capable of providing automated Bi-Directional Testing

Certification:

• Certify that End-to-End loss of a fiber span meets loss budget
• Certify that Optical Return Loss (ORL) meets specs.
• Uses PC software for documentation and certification reporting

Troubleshooting:

• Verify continuity of a fiber span
• Verify correction of ORL issues

Recommended Equipment:

FIS Fiber Optic Test Set Kit
EXFO 930 Max Tester