The ONS 15454 automatic power control (APC) feature performs the following functions:
Note APC algorithms manage the optical parameters of the OPT-BST, OPT-PRE, OPT-AMP-17-C, 32DMX, 40-DMX-C, 40-DMX-CE, 40-SMR1-C, 40-SMR2-C, OPT-BST-L, OPT-AMP-L, OPT-AMP-C, and 32DMX-L cards.
Amplifier software uses a control gain loop with fast transient suppression to keep the channel power constant regardless of any changes in the number of channels. Amplifiers monitor the changes to the input power and change the output power proportionately according to the calculated gain setpoint. The shelf controller software emulates the control output power loop to adjust for fiber degradation. To perform this function, the TCC2/TCC2P/TCC3/TNC/TSC needs to know the channel distribution, which is provided by a signaling protocol, and the expected per channel power, which you can provision. The TCC2/TCC2P/TCC3/TNC/TSC card compares the actual amplifier output power with the expected amplifier output power and modifies the setpoints if any discrepancies occur.
12.8.1 APC at the Amplifier Card Level
In constant gain mode, the amplifier power out control loop performs the following input and output power calculations, where G represents the gain and t represents time.
Pout (t) = G * Pin (t) (mW)
Pout (t) = G + Pin (t) (dB)
In a power-equalized optical system, the total input power is proportional to the number of channels. The amplifier software compensates for any variation of the input power due to changes in the number of channels carried by the incoming signal.
Amplifier software identifies changes in the read input power in two different instances, t1 and t2, as a change in the traffic being carried. The letters m and n in the following formula represent two different channel numbers. Pin/ch represents the input power per channel.
Pin (t1)= nPin/ch
Pin (t2) = mPin/ch
Amplifier software applies the variation in the input power to the output power with a reaction time that is a fraction of a millisecond. This keeps the power constant on each channel at the output amplifier, even during a channel upgrade or a fiber cut.
The per channel power and working mode (gain or power) are set by automatic node setup (ANS). The provisioning is conducted on a per-side basis. A preamplifier or a booster amplifier facing Side i is provisioned using the Side i parameters present in the node database, where i - A, B, C, D, E, F, G, or H.
Starting from the expected per channel power, the amplifiers automatically calculate the gain setpoint after the first channel is provisioned. An amplifier gain setpoint is calculated in order to make it equal to the loss of the span preceding the amplifier itself. After the gain is calculated, the setpoint is no longer changed by the amplifier. Amplifier gain is recalculated every time the number of provisioned channels returns to zero. If you need to force a recalculation of the gain, move the number of channels back to zero.
12.8.2 APC at the Shelf Controller Layer
Amplifiers are managed through software to control changes in the input power caused by changes in the number of channels. The software adjusts the output total power to maintain a constant per channel power value when the number of input channel changes.
Changes in the network characteristics have an impact on the amplifier input power. Changes in the input power are compensated for only by modifying the original calculated gain, because input power changes imply changes in the span loss. As a consequence, the gain to span loss established at amplifier start-up is no longer satisfied, as shown in Figure 12-23.
Figure 12-23 Using Amplifier Gain Adjustment to Compensate for System Degradation
In Figure 12-23, Node 1 and Node 2 are equipped with booster amplifiers and preamplifiers. The input power received at the preamplifier on Node 2 (Pin2) depends on the total power launched by the booster amplifier on Node1, Pout1(n) (where n is the number of channels), and the effect of the span attenuation (L) between the two nodes. Span loss changes due to aging fiber and components or changes in operating conditions. The power into Node 2 is given by the following formula:
Pin2 = LPout1(n)
The phase gain of the preamplifier on Node 2 (GPre-2) is set during provisioning in order to compensate for the span loss so that the Node 2 preamplifier output power (Pout-Pre-2) is equal to the original transmitted power, as represented in the following formula:
Pout-Pre-2 = L x GPre-2 x Pout1(n)
In cases of system degradation, the power received at Node 2 decreases due to the change of span insertion loss (from L to L'). As a consequence of the preamplifier gain control working mode, the Node 2 preamplifier output power (Pout-Pre-2) also decreases. The goal of APC at the shelf controller layer is simply to detect if an amplifier output change is needed because of changes in the number of channels or to other factors. If factors other than changes in the number of channels occur, APC provisions a new gain at the Node 2 preamplifier (GPre-2') to compensate for the new span loss, as shown in the formula:
GPre-2' = GPre-2 (L/ L') = GPre-2 + [Pout-Pre-2 –Exp(Pout-Pre-2)]
Generalizing on the above relationship, APC is able to compensate for system degradation by adjusting working amplifier gain or variable optical attenuation (VOA) and to eliminate the difference between the power value read by the photodiodes and the expected power value. The expected power values are calculated using:
- Provisioned per channel power value
- Channel distribution (the number of express, add, and drop channels in the node)
- ASE estimation
Channel distribution is determined by the sum of the provisioned and failed channels. Information about provisioned wavelengths is sent to APC on the applicable nodes during circuit creation. Information about failed channels is collected through a signaling protocol that monitors alarms on ports in the applicable nodes and distributes that information to all the other nodes in the network.
ASE calculations purify the noise from the power level reported from the photodiode. Each amplifier can compensate for its own noise, but cascaded amplifiers cannot compensate for ASE generated by preceding nodes. The ASE effect increases when the number of channels decreases; therefore, a correction factor must be calculated in each amplifier of the ring to compensate for ASE build-up.
APC is a network-level feature that is distributed among different nodes. An APC domain is a set of nodes that is controlled by the same instance of APC at the network level. An APC domain optically identifies a portion of the network that can be independently regulated. An optical network can be divided into several different domains, with the following characteristics:
- Every domain is terminated by two node sides. The node sides terminating domains are:
– Terminal node (any type)
– ROADM node
– Hub node
– Cross-connect (XC) termination mesh node
– Line termination mesh node
- APC domains are shown in both Cisco Transport Controller (CTC) and Transaction Language One (TL1).
- In CTC, domains are shown in the network view and reported as a list of spans. Each span is identified by a node/side pair, for example:
APC Domain Node_1 Side A, Node_4 Side B
+ Span 1: Node_1 Side A, Node_2 Side B
+ Span 2: Node_2 Side A, Node_3 Side B
+ Span 3: Node_3 Side A, Node_4 Side B
- APC domains are not refreshed automatically; instead, they are refreshed using a Refresh button.
Inside a domain, the APC algorithm designates a master node that is responsible for starting APC hourly or every time a new circuit is provisioned or removed. Every time the master node signals APC to start, gain and VOA setpoints are evaluated on all nodes in the network. If corrections are needed in different nodes, they are always performed sequentially following the optical paths starting from the master node.
APC corrects the power level only if the variation exceeds the hysteresis thresholds of +/– 0.5 dB. Any power level fluctuation within the threshold range is skipped since it is considered negligible. Because APC is designed to follow slow time events, it skips corrections greater than 3 dB. This is the typical total aging margin that is provisioned during the network design phase. After you provision the first channel or the amplifiers are turned up for the first time, APC does not apply the 3 dB rule. In this case, APC corrects all the power differences to turn up the node.
To avoid large power fluctuations, APC adjusts power levels incrementally. The maximum power correction is +/– 0.5 dB. This is applied to each iteration until the optimal power level is reached. For example, a gain deviation of 2 dB is corrected in four steps. Each of the four steps requires a complete APC check on every node in the network. APC can correct up to a maximum of 3 dB on an hourly basis. If degradation occurs over a longer time period, APC compensates for it by using all margins that you provision during installation.
If no margin is available, adjustments cannot be made because setpoints exceed the ranges. APC communicates the event to CTC, Cisco Transport Manager (CTM), and TL1 through an APC Fail condition. APC clears the APC fail condition when the setpoints return to the allowed ranges.
APC can be manually disabled. In addition, APC automatically disables itself when:
- An Hardware Fail (HF) alarm is raised by any card in any of the domain nodes.
- A Mismatch Equipment Alarm (MEA) is raised by any card in any of the domain nodes.
- An Improper Removal (IMPROPRMVL) alarm is raised by any card in any of the domain nodes.
- Gain Degrade (GAIN-HDEG), Power Degrade (OPWR-HDEG), and Power Fail (PWR-FAIL) alarms are raised by the output port of any amplifier card in any of the domain nodes.
- A VOA degrade or fail alarm is raised by any of the cards in any of the domain nodes.
- The signaling protocol detects that one of the APC instances in any of the domain nodes is no longer reachable.
The APC state (Enable/Disable) is located on every node and can be retrieved by the CTC or TL1 interface. If an event that disables APC occurs in one of the network nodes, APC is disabled on all the other nodes and the APC state changes to DISABLE - INTERNAL. The disabled state is raised only by the node where the problem occurred to simplify troubleshooting.
APC raises the following minor, non-service-affecting alarms at the port level in CTC, TL1, and Simple Network Management Protocol (SNMP):
- APC Out of Range—APC cannot assign a new setpoint for a parameter that is allocated to a port because the new setpoint exceeds the parameter range.
- APC Correction Skipped—APC skipped a correction to one parameter allocated to a port because the difference between the expected and current values exceeds the +/– 3 dB security range.
- APC Disabled—APC is disabled, either by a user or internal action.
After the error condition is cleared, the signaling protocol enables APC on the network and the APC DISABLE - INTERNAL condition is cleared. Because APC is required after channel provisioning to compensate for ASE effects, all optical channel network connection (OCHNC) and optical channel client connection (OCHCC) circuits that you provision during the disabled APC state are kept in the Out-of-Service and Autonomous, Automatic In-Service (OOS-AU,AINS) (ANSI) or Unlocked-disabled,automaticInService (ETSI) service state until APC is enabled. OCHNCs and OCHCCs automatically go into the In-Service and Normal (IS-NR) (ANSI) or Unlocked-enabled (ETSI) service state only after APC is enabled.
Lan Topologies Assignment Essay example
1325 WordsJun 12th, 20146 Pages
February 8, 2014
February 8, 2014
LAN Topologies Assignment
Case Project 2-1
You have been hired to upgrade a network of 50 computers currently connected to 10 Mbps hubs. This long-overdue upgrade is necessary because of poor network response time caused by a lot of collisions occurring during long file transfers between clients and servers. How do you recommend upgrading this network? What interconnecting devices will you use, and what benefit will you get from using these devices? Write a short memo describing the upgrade and, if possible, include a drawing of the new network.
I have been recently hired to upgrade a company’s current network. Currently this company has a 10BaseT network established (Regan, 2004). This client is…show more content…
Component needed will be; five 24 port switches, Cat5e UTP and the workstation computers with the proper NIC devices. This layout would start with the 24 port switch in the center of the network. This switch is connected using a Cat5e UTP medium to the other 5 switches. Each switch is connected to the workstation computers using Cat5e UTP medium. This will create a physical star topology. The logical topology will be based on a 100BaseTX and incorporate the use TCP/IP protocol.
Case Project 2-2
Two hundred workstations and four servers on a single LAN are connected by a number of switches. You’re seeing an excessive number of broadcast packets throughout the LAN and want to decrease the effect this broadcast traffic has on your network. What steps must you take to achieve this goal?
I have been recently hired to upgrade a company’s current network. Currently this company has two hundred workstations and four servers on a single LAN. Furthermore, my client is having issues with excessive number of broadcast traffic on the network. I believe the overall issue with the LAN is too much traffic on a single network, to fix this problem their single LAN needs to be broken up into four different networks and then have each individual LAN routed into one another. This will create an extended star physical topology. A total of one router, seven 48 port switches, and CAT5e UTP are