optical fiber CWDM

[Anamika Basnotra]

can anyone of u tell what difference is between normal optical fiber and optical fiber CWDM
whether to use coarse or dense WDM, it all depends on WDM not on fiber
anyone having any knowledge about optical fiber CWDM

[Dr Rk Sethi]

Hi Anamika,
Coarse WDM (CWDM) in comparison to conventional WDM and DWDM employs increased spacing of the channel to permit less sophisticated and cheaper transceiver designs.

[Ravil]

Hi Anamika,

The explanation about difference between two techniques was given by Rk Sethi. According to the types of fibers used, I would add that, since DWDM systems are more proned to nonlinear effects then CWDM systems do, fibers designed for DWDM systems will definitely have a larger effective core area than CWDM systems.

[Anamika Basnotra]

bt the technique CWDM or DWDM was designed so that we can use the existing optical fiber more efficiently
what about CWDM fiber, are they designed for creating new optical links; if so, then why DWDM fiber is not available in the system?

[Ashu verma]

And if go to more less channel spacing i.e 12Ghz and less them which fiber we can use.
As ravil said ,we increase the core area for DWDM system,can we increase it by own.
Is there any fixed standards to set the core area of fiber????

[Ravil]

Hi Sam Sung, just a few comments about your question according to fiber core. It is obvious that you can not increase the core size of the fiber since it was produced, – you are right about that. And this core size is specified by radius (or diameter) for different types of fibers in corresponding standards of ITU-T. What I was talking about is EFFECTIVE CORE AREA which is defined by beam radius of Gaussian light pulse propagating through the fiber. For example, in large-effective area fibers (LEAF) the EFFECTIVE CORE AREA is increased intentionally to reduce the impact of fiber nonlinearity.

[Ravil]

Dear Anamika and Sam Sung,

I just want to clarify my point first. You are right, Anamika, it is preferable to use the existing fiber optical links due to reasons of economical efficiency. When I was answering your question about the differences between DWDM and CWDM, I meant the large effective area fibers would be more efficient from design point of view. The difference DWDM and CWDM for existing fiber optical links is the trade-off between the capacity (higher in DWDM) and “reach” (higher in CWDM).

[Ravil]

According to Sam Sung’s questions I should clarify few things as well. First, you are right: the spacing in DWDM and CWDM systems is standardized mainly for given bit rate (not sure which bit rate you are planning to use for 12GHz). The increment of the channels number will bring several limitations with it. The main of them are nonlinear effects influence. Hence, these effects needs to be considered in system performance not just by changing the fiber but by using corresponding compensations!

[Anamika Basnotra]

thnkew ravil for such an explaination
can u clarify one more thing
optical fiber CWDM must be specially designed fibers
do they really exist in real world? i mean there is no informstion realted to them on google

[Ravil]

You are welcome, Anamika!

According to your last question about the existence of CWDM and DWDM fibers, I can tell you from my experience that I didn’t hear such specific names and don’t think that the specific fibers with such names are existing. As I have noticed above, the main difference in design of fibers for CWDM and DWDM will be high requirements for mitigation of nonlinearities in DWDM systems. By the way, when did you obtain these particular names from? Can u share you source, please?

[Anamika Basnotra]

u are scaring me
in the component library of optisystem, we have three types of optical fibers na
optical fiber, bidirectional optical fiber and optical fiber CWDM
what is the meaning of ‘optical fiber CWDM’
and optisystem is based on the realistic modeling of fiber-optic
communication systems.
so by this definition this type of fiber should also exist

[Ravil]

Dear Anamika,
there is nothing to be scare about:). I meant that these names are not common in practice and didn’t hear them as official names. Since in OptiSystem we are working with simulation models, there is a model of optical fiber optimized for CWDM which is optimized in CWDM window in terms of its calculation limits (I didn’t see any models for DWDM) in comparison, for example, with a general model for optical fibers. In other words these fibers exist but under different names, for instance LEAF, NZDSF, etc.
I hope that Optiwave team will correct me if I am wrong…

[Anamika Basnotra]

thnkew ravil
i understood your point

[Ravil]

You are welcome! You have raised a very good question! Please, let me know you will learn more about it or if I have a misleading point…

[Anamika Basnotra]

yeah ofcource Rvail
the thing introduced in this fiber is ‘cross phase modulation’
the doubt here is why is CWDM written with its name. it must be having some special significance
n if u get to know anything related to this, plz let me know

[Dr Rk Sethi]

Hi Anamika,
The concept of Course WDM (CWDM) emerged from the combination of the production of full spectrum ( low water content) G.652C and G.652D fibers, the development of relatively inexpensive optical sources, and the desire to have low cost optical links operating in access networks and local area networks.
in 2002 the ITU-T released recommendation G.694.2 which defined the spectral grid for CWDM. the CWDM grid is made up of 18 wavelengths defined within the range 1270nm to 1610 nm (O- through L-band) spaced by 20 nm with wavelength drift tolerances of +/-2nm. this can be achieved with inexpensive light sources that are not temperature controlled.
For more detail you can refer –
Y Liu, A R Davies, J D Ingham, R V Penty, and I H White, “uncoded DBR laser directly modulated at 3.125 Gbps as an athermal transmitter for low cost WDM systems,” IEEE Photonics Technol. Lett., vol. 17, pp2026-2028, Oct 2005.

Optical Fiber communications by Gerd Keiser, Mc Graw Hills

[Anamika Basnotra]

thnkew Mr. Sethi
u cleared many of my doubts
bt the link which u provided doesnot match any of the paper in the IEEE library
can u provide some more information; it will be really helpful

[Dr Rk Sethi]

Hi Anamika,
Just follow the link to get the paper.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1512261&isnumber=32382

Yiran Liu; Davies, A.R.; Ingham, J.D.; Penty, R.V.; White, I.H., “Uncooled DBR laser directly Modulated at 3.125 gb/s as athermal transmitter for low-cost WDM systems,” Photonics Technology Letters, IEEE , vol.17, no.10, pp.2026,2028, Oct. 2005
doi: 10.1109/LPT.2005.856367
Abstract: An uncooled three-section tunable distributed Bragg reflector laser is demonstrated as an athermal transmitter for low-cost uncooled wavelength-division-multiplexing (WDM) systems with tight channel spacing. A ±0.02-nm thermal wavelength drift is achieved under continuous-wave operation up to 70°C. Dynamic sidemode suppression ratio of greater than 35 dB is consistently obtained under 3.125-Gb/s direct modulation over a 20°C-70°C temperature range, with wavelength variation of as low as ±0.2 nm. This indicates that more than an order of magnitude reduction in coarse WDM channel spacing is possible using this source.
keywords: {channel spacing;distributed Bragg reflector lasers;optical modulation;optical transmitters;semiconductor lasers;wavelength division multiplexing;20 to 70 degC;3.125 Gbit/s;DBR laser;athermal transmitter;channel spacing;coarse WDM;continuous-wave operation;direct modulation;dynamic sidemode suppression ratio;low-cost WDM systems;semiconductor lasers;thermal wavelength drift;three-section laser;tight channel spacing;tunable laser;uncooled laser;wavelength variation;Channel spacing;Distributed Bragg reflectors;Erbium-doped fiber lasers;Gratings;Laser tuning;Optical transmitters;Semiconductor lasers;Temperature control;Temperature distribution;Wavelength division multiplexing;Direct intensity modulation;optical fiber communications;semiconductor lasers;tunable lasers;wavelength-division-multiplexing (WDM) applications},

[Anamika Basnotra]

thankyou so much sir

[Dr Rk Sethi]

Welcome Anamika

[Author]

Posts