The france-Corsica line ( more than 300 km) used to be without repeater. However as the others said, for long haul line, there is one EDFA each 80-100km (not that up to date, maybe new stuff exist)
Romain
Romain Peretti · 19.26 · 27.19 · Ecole Centrale de Lyon
The france-Corsica line ( more than 300 km) used to be without repeater.
The transmitted power must be high for that link, is it?
For a given fiber type (e.g. single-mode G652), It depends on many parameters such as the wavelength used, the bit rate (assuming digital transmission) and the BER required, which strongly depends on the modulation scheme.
For standard NRZ-OOK links with G652 fibers, the unamplified limit is approximately 100 km. I strongly suggest to use an optical transmission simulator (e.g. VPI transmission maker, optisystem, optsim) to check this limit under varying physical conditions.
Is that 80-100 km distance only consist of fiber optic cable without using any splices or connectors?
Again, be careful with the bit-rate and chromatic dispersion (CD).
As an example, If you wish to transmit 40 Gbit/s with a non CD-compensated and unamplified link, then, the maximum distance will be limited to about 20 km due to intersymbol-interference caused by CD. Then, if you increase the optical power using a higher input power, you'll experience non-linear effects, as noticed by Shridhar Iyer.
@Volodymyr and Sridhar : Fusion splice is it?
@Bruno : As I know, the CD only occurs on multimode, and for the singlemode, we can ignore it. (I'm sorry if I'm wrong).
Want to add a question, if I want to use an OTDR with power output -10 dBm and 10us pulse, to measure a 50 km length link, how much dynamic range should I use?
Some time ago, I seem to remember distances of 400km +, demonstrated in lab conditions with a single wavelength channel, but these kind of distances are only really useful for undersea links, as one usually benefits from having access to data at shorter intermediate distances.
The launched power at the transmit end, is limited by fibre nonlinearity, which dominantly occurs at the launch end.
The power required at the receiver depends on bit rate: Equivalent systems require similar numbers of photons (i.e.energy) per bit, so doubling the bit rate requires twice the average received power. Assuming a fibre loss of 0.2 dB / km fibre loss, this means the distance reached is reduced by 15km for every doubling in bit rate (15km x 0.2dB/km = 3dB, i.e. a factor of 2).
@ stevan : be careful, chromatic dispersion DOES NOT only occur in multimode fibers, where waveguide dispersion is another impairment.
In standard mode fibers (e.g. G652), the CD value is 17 ps/nm/km, which means that over 100 km, the signal distorsion (optical "bits") may reach 1700 ps/nm.
Hence, the optical line must contain CD compensators, either in the form of CD fibers (negative dispersion parameter) or bragg gratings.
Re: Chromatic Dispersion Compensation:
The latest highest performance systems use coherent detection at the receiver, so can compensate signal distortions including Chromatic Dispersion at the receiver using some heavy signal processing. Aloso, perhaps couner-intuitively, the effects of nonlinearity in the fibre are reduced by not compensating the dispersion at intermediate distances along the way (the dispersion de-phases the nonlinearly generated products). Coherent detection in optical systems is like a superhet radio, by mixing the small received signal with a much bigger local oscillator signal (laser), at the photodetector, one can extract all the signal information in amplitide and phase.
Quite right, Richard .... but the implementation of a coherent link is a little bit more tricky and complex than the direct detection one.
A few years ago in a real network with SMF fiber we have achieved distance over 120 km (2.5 Gb / s). It certainly depends on the bit rate and the quality of the splices and the total attenuation of distance. It also depends on the power of the transmitter and receiver quality.
Can someone help me solve this problem? I've already posted it in here :
https://www.researchgate.net/post/Is_it_okay_to_use_this_reflection_formula_to_calculate_the_spike_reflection_at_OTDR
Thanks.
The maximum distance of optical link first depends on the quality of the fiber used as a medium of transmission and the insertion losses of sub-systems utilized along the link. These factors mainly limit the span the the optical repeaters required for a designed link.
Not to forget that the number splice joints and their qualities are counted.
The maximum achievable transmission span depends on many factors. It depends on the type of the fibre, electrical data rate, electro-optic modulation format, optical launch power and the fibre non-linear and linear impairments. Mentioning an exact achievable distance is only acceptable for a specific type of setup and the condition mentioned above should be very carefully considered. So the answer will not be an exact number and will vary rather significantly to the criteria mentioned above.
@ Bahrami: Right, to be more specific better to say optical data rate which is counted as Mb/s*km.
Maximum length depends on various parameters such as bit error rate and input power inside the fiber. we can calculate the maximum length with the below formula:
The question states no amplifier or repeater. If the intention was to mean "in-line" then this allows the use of Raman scattering to provide end pumped amplification.
Kumar's formula is for a purely loss limited transmission with a direct detection receiver. In practice there may be penalties from dispersion which can be compensated for either optically before the receiver or electrically using coherent receivers (for which Kumar's formula does not apply).
Anwar's answer of 100km is typical for unamplified and uncompensated systems of bit rate around 10Gb/s.
Demonstrations of systems involving end pumping have achieved results of around 400km.
Keith Sir u are right. But in general or practical point of view what distance should we take?
Vikram,
I think your answer made the right point: it depends on various parameters and assumptions. There is no single answer to the question as stated.
Dear friend, Cisco's has done Documentation concerning the SFP Gigabit Interface. Hope the following link might help….
https://www.cisco.com/c/en/us/products/collateral/interfaces-modules/gigabit-ethernet-gbic-sfp-modules/product_data_sheet0900aecd8033f885.html
OR refer the attached pdf...
15 kilometers or about 9.32 miles. This is without regeneration or repeater.
Hello Stevan, the length is limited by different aspects not only attenaution but chromatic dispersion, PMD, and nonlinear effects if the scenario is WDM or a high launching power, besides with high bit rates the problem degrades severely the performance and obviosuly restrict the span length. In the attach you can find restriction due to linear effects.
https://www.ccontrols.ch/cms/upload/content/aktionen/PDF/2013-04-05_Chromatic_Dispersion.pdf
Regards
- Badges
- Science topic
- Similar topics
- Geoscience
- Atmospheric Sciences
- Climate Science
- Climate Change