How to Uncrease the Bandwidth in Same Fiber

To increase the bandwidth in same fiber we can use several modulation techniques which can offer high spectral efficiency and high receiver sensitivity. In Oder to increase the bandwidth in we can go for different multiplexing techniques. Wavelength division multiplexing (WDM), has proven more cost effective in many instances. It allows using current electronics and current fibers, but simply shares fibers by transmitting different channels at different wavelengths of light. Systems that already use fiber optic amplifiers as repeaters also do not require upgrading for most WDM systems. But nowadays people use Dense Wavelength Division Multiplexing, using that we can increase the bandwidth,

Dense Wavelength Division Multiplexing

For submarine cables, DWDM enhances the capacity without adding fibers, which create larger cables and bulkier and more complicated repeaters. DWDM is designed for long-haul transmission where wavelengths are packed tightly together. Vendors have found various techniques for cramming 32, 64, or 128 wavelengths into a fiber. In this each wave length, we can store different data types (STM4 or STM 5) and can transmit it. This compression exposes to carry more bandwidth at the transmitting end when multiplexing. Since each channel is demultiplexed at the end of the transmission back into the original source, different data formats being transmitted at different data rates can be transmitted together.

    Throughout this article I hope you may get some thing. This provides very basic explanation and future will cover more. Comments are well come. Thank you.

Important Factors of designing a Optical Fiber submarine cable

Type of optical fiber – when we are designing a cable for submarine cable, we have to select proper fiber type for the network. Most suitable fiber optic type for this network is” standard single mode fibers (G654) “which are having almost zero dispersion at 1300 nm is suitable for long distance fiber optical links.

Dispersion - We know submarine cable has very high length; therefore the main interference to the system is dispersion. To avoid that, we can use DCF fibers at regular places.

Reliability - The reliability of submarine cables is so important and it needs to be high strength. Especially in the point of splicing. It is in the see, thus we can’t maintain the cable day by day.

Transmitting power – Transmitting power is also very important In a SEA-WE-ME 4 cable, we need to supply better and sufficient transmitting power to the source. Because of the attenuation of the signal is high when it is travelling high distance through under the see. And also we need to maintain sufficient power for repeaters through the cable.

Source type - For high-data-rate applications as like this, we can use semi conductor laser diode (SLD). Because it gives narrow spectral width, directivity, higher transmitting power etc makes it most suitable for long distance transmission.

Receiver sensitivity - We know in a long haul communication the transmitting signal is attenuated. Then the receiver gets weak signal. Therefore it should have the high receiver sensitivity for grab the receiving signal.

Detector type - Through SEA-WE-ME 4 cable, signals are traveling more distance. Therefore we need detector with higher sensitivity. Therefore we can use Avalanche photo diode (APD).

Bit Error rate - When the signal travels through SEA-WE-ME 4 cable there are many inter symbol interferences. It confuses the receiving data. Therefore bit error happens. In order to avoid bit errors we need to reduce the base band data rate. But it is difficult to reduce the data rate because we nee high data rate.

Number of connectors - When we have number of amplifiers and repeaters we also introduce loss to the system by increasing number of connectors. And also SEA-WE-ME 4 cable is connected to 14 countries. Here also we need to setup connector. These losses will reduce the length of the high bit rate long haul fiber optical links. Therefore it is better keep the connecters in a low number.

Number of splicing points - In this SEA-WE-ME 4 cable it has length of 20,000 km. therefore it may need 10,000 splices if we use 2km cable. And we know each splicing point introduce a loss to the system. But we can’t control when the link is rising.

    Throughout this article I hope you may get some thing. This provides very basic explanation and future will cover more. Comments are well come. Thank you.