Lumina "sucita" transmite mai multa informatie (Twisted light transmits more data)

Un nou cablu din fibra optica care transmite mai multe raze de lumina simultan poate usura si  grabi drastic viteza informatiei transmise pe internet.

Andrew Weiner, un fizician de la Universitatea Purdue din West Lafayette, Indiana spune ca:" E ca si cum am avea mai multe fibre optice insa fara a avea cu adevarat mai multe"

Companiile de telecomunicatii folosesc lumina pentru a codifica si transmite informatia prin cablurile din fibra optica. In ultimele decenii, savantii au marit latimea de banda prin faptul ca au permis fasciculului de lumina sa transmita mai multa informatie, dar progresul lor va fi depasit in curand de vastele cantitati de informatie pe care oamenii le schimba intre ei. Folosind mai multe fibre ar fi costisitor. Siddharth Ramachandran, fizician de la Universitatea Boston spune ca: "Am ajuns la punctul unde comunitatea telecomunicatiilor a inceput sa intrebe ce altceva am putea face".

Solutia pe care a gasit-o impreuna cu echipa lui este sa trimita mai multe raze de lumina simultan intr-o singura fibra. Aceasta idee e aparut acum 40 de ani , dar nu este un lucru usor de facut deoarece fibrele traditionale permit razelor de lumina ce se misca in paralel sa se amestece incurcand 1s si 0s codate in fiecare fascicul.

Recent, cercetatorii au incercat sa imparta torsiunile in unele dintre fascicule pentru ca ele sa formeze o spirala impreuna cu fibra, in timp ce celelalte circula in linie dreapta, dar nici acest lucru nu a mers.

Abandonand ideea "amestecarii" luminii, cativa dintre cercetatori au creat algoritmi complecsi care descifreaza fasciculele amestecate la capatul cablului, dar algoritmii sunt lenti si nu sunt eficienti 100%.

Pe 28 Iunie, Ramachandran si echipa lui au raportat construirea unei fibre lungi de 1,1 km, care, pentru rima oara, permitea multiplelor fascicule sa ajunga la destinatie intacte. Fibrele lor de siliciu sunt narcotizate  cu alte materiale, fapt ce permite fasciculelor sa se miste la viteze usor diferite si le impiedica sa se amestece.

Folosind un instrument numit "modulator de lumina spatiala" pentru a rasuci fasciculele, cercetatorii au trimis 4 fascicule concomitent, trimitand informatie de mai multe de 1.6 trilioane de biti pe secunda, prin fibra lor facuta la comanda. Ei spera sa comprime mai multa informatie  in fiecare din fascicule folosind metode deja exploatate de industria telecomunicatiilor. Ramachandran a observat ca echipa sa si-a fabricat fibrele folosind metode standard, astfel ca, daca vor fi produse la scara industriala fibra nu ar trebui sa coste mai mult decat cele deja disponibile.

Ramachandran spune ca nu este sigur daca noua fibra va putea fi utilizata pentru a comunica informatia pe distante mari ,dar spera ca va imbunatati transmisia in zonele cu populatie densa. De asemenea va ajuta la vastele servere ale fermelor de informatie, unde mii de computere stocheaza  informatii pentru cmpanii ca Google si Facebook care necesita retele ferme si rapide pentru a schimba informatii.

A new fiber-optic cable that seamlessly shuttles multiple beams of light simultaneously could drastically speed data transfer over the Internet.

“It’s like having more fibers without actually laying more fibers,” says Andrew Weiner, a physicist at Purdue University in West Lafayette, Indiana.

Telecommunications companies use light to encode and send data through fiber-optic cables. Over the last few decades, scientists have increased bandwidth by enabling a single beam to carry more information, but their progress soon will be outpaced by the vast amounts of data people exchange. Laying more fibers would be expensive. “We’ve gotten to the point where the [telecom] community has been asking what else we can do,” says Siddharth Ramachandran, a physicist at Boston University.

The solution he and his team came up with was to dispatch multiple beams of light through a single fiber. The idea goes back nearly four decades, but it’s not an easy thing to do because traditional fibers allow light beams moving in parallel to interfere with each other, jumbling the 1s and 0s encoded in each beam.

Recently, scientists have tried imparting twists into some of the beams so that they spiral along the fiber while others travel in a straight line, but that hasn’t worked either. Resigned to this light mixing, some researchers have created complex algorithms that decipher the amalgamated beams at the end of the cable, but the algorithms are slow and not 100 percent effective.

In the June 28 Science, Ramachandran and his team report building a 1.1-kilometer-long fiber that, for the first time, allows multiple beams to reach their destination intact. Their silica fiber is doped in places with other materials, which cause the beams to move at slightly different speeds and prevent them from mixing with each other.

Using an instrument called a spatial light modulator to twist the beams, the researchers sent as many as four concurrent beams, transmitting data at speeds up to 1.6 trillion bits per second, through their custom fiber. They hope to squeeze more data into each of those beams using methods already exploited by the telecom industry. Ramachandran notes that the team manufactured its fiber at a commercial facility using standard methods, so if it were mass produced, the fiber should not cost much more than those now in use.

Ramachandran says he is unsure whether the new fiber will work for communicating data over long distances, but hopes that it will improve transmission in dense metropolitan areas. It could also help in vast data server farms, where thousands of computers that store data for companies like Google and Facebook require tight, fast networks to exchange information.