Variable Optical Power Splitters in PON application


Accelink's VOPS is an innovative variable optical power splitter that based on birefringent materials and polarization beam management. Prototypes of such devices have shown low insertion loss, polarization independence, and full variable range. In fact, prototypes of 1x2 and 1x4 variable OPSs using this technology have been constructed in both electronic and manual tune versions. The splitters can find use in a variety of applications.

Features

• Variable OPS will improve network scalability, increase optical power efficiency, provide better network reliability, and lower investment risk;
• When all user are connected serially, Variable OPSs can equalize the power delivered;
• The furthermost user has the biggest optical power loss as well as the greatest possibility of being disturbed. Variable OPSs can allocate more optical power to the users farther from the OLT to strengthen their anti-jamming ability.

Other Information

• VOPS Application in Self-healing PON Rings
  
  
  
  Self-healing rings are a popular protection mode in the MAN. The double fiber ring PON architecture shown above is an ideal application of the variable OPS.
  1) The network architecture comprises a first set of N serially connected power-splitting centers connected at one end to receive a power signal and at another end to a termination point. Each splitting center has an output associated with a sub-network for delivering a portion of the power signal to that sub-network, wherein the power-splitting factor in each power-splitting center is variable. Thus, the portion of the power signal delivered to each sub-network is tunable;
  2) A second set of N serially connected power-splitting centers is connected in the same way. But each of these centers is associated with one of the first set of optical splitting centers such that the nth power-splitting center of the first set is associated with the (N-n+1)th of the second set. In addition, each pair of power-splitting centers has a respective output connected to a common sub-network, wherein only one of each pair of power-splitting centers receives the power signalӣ
  
  
• VOPS in Hierarchial PON Application
  
  
  
  1) With the arrival of variable OPSs, carriers can now use a hierarchical connected architecture. In this kind of architecture, many users share one ONU, and many ONUs converge at one OLT through the OPSs. The number of users in each ONU can be different, and the path distances of each ONU to the OLT can be different too. Therefore, the optical-signal power of each ONU can be very different and can vary each moment.
  2) The variable OPS can provide many benefits for such an architecture. It can allocate the optical power of each ONU dynamically by changing its own power split ratio, improve network scalability, increase optical power efficiency, and provide better network reliability.
  3) Variable OPSs have other benefits for FTTH applications, including the allocation of power to each node according to its needs. By using variable OPSs, the initial equipment investment and installation cost can be economized based on the principle of distribution on demand.
  
  
• VOPS in Long Haul Application
  
  
  
  Variable OPSs also can play important roles in long-haul node-to-node networks. For instance, it can be used in optical line protection (OLP). There are two OLP schemes presently deployed: 1+1 and 1:1.
  
  For 1+1 protection, a 1x2 optical splitter at the transmit end divides the signal for transmission over two paths. The receive end receives the signal from both routes and selects one of the two signals with another 1x2 optical switch. The advantage is that the system can monitor both routes at the same time and always selects the ”°best”± signal. But the scheme always means 50% optical power loss.
  
  The 1:1 protection approach requires an 1x2 optical switch at both the transmit and receive end. The optical signal is transmitted only in one route at the same time, so that the system avoids the loss of half of the optical power at the start.
  
  Above image illustrates how using variable OPSs to replace the 1x2 optical switches in the 1+1 approach can provide the advantages of both protection schemes. The system can transfer the optical power resource on the secondary path dynamically and monitor both paths at the same time.
  
  Furthermore, sometimes the primary and secondary paths are not in the same cable-perhaps not even in the same physical path-so protection can be provided in case of a cable break.When the variable OPS is introduced, the variable optical power attenuator is no longer necessary; the requirement for the OA would vary depending on the application.
  
  
• VOPS Application in Optical Amplifier Efficiency Improvement
  
  
  
  High-power amplifiers are widely deployed for fiber cable TV networks, using variable OPSs to replace common optical splitters will be convenient for network construction, lower cost, and provide better reliability and scalability.
  
  Variable OPSs can also play a key role in the design of intelligent Oas.For example, an economical self-consistent bidirectional OA design is shown in above picture. This dual-channel amplifying module can be used in a terminal line card to amplify both receiving and transmitting channels at the same time.By adjusting the power split ratio, the variable OPS can provide flexibility for optical networks to maintain power equilibrium, make use of optical resources effectively, and maintain the quality of network transmission.