瑞士洛桑聯(lián)邦理工學院(EPFL)的研究團隊宣稱找到一種簡單的創(chuàng)新途徑，只需輕松地切換至新的發(fā)射器，即可使現(xiàn)有網(wǎng)絡中的光纖傳輸率提高10倍。根據(jù)EPFL的研究人員Camille Bres與Luc Thevenaz指出，采用奈奎斯特正弦脈沖，可在時域重迭且采用最小帶寬的脈沖上為信息進行編碼，從而實現(xiàn)最大化的光纖傳輸率。
由于脈沖能盡可能減少符號間的干擾，其他研究團隊也試圖產(chǎn)生奈奎斯特正弦脈沖，但最后還都得再采用更復雜的訊號產(chǎn)生器。Camille Bres與Luc Thevenaz則聲稱其光譜合成技術能更有效地操作，而且也是唯一能簡單建置商用光纖發(fā)射器的技術。
“我們合成出一種能帶來完美脈沖波形的頻譜。透過使用簡單的強度調(diào)變器產(chǎn)生一組光譜線，有規(guī)率地留出間隔，并顯現(xiàn)完全相同的振幅與相位。這是在時域中自動產(chǎn)生的正弦脈沖波形，”Luc Thevenaz表示，“這非常簡單明了，但以前都沒人想過要這樣做?！?
以奈奎斯特脈沖編碼10倍信息容量的概念圖
Source：Jamani Caillet / EPFL3O3esmc
EPFL的研究團隊宣稱，在實驗室環(huán)境下，雷射與調(diào)變器可產(chǎn)生較廣的頻譜脈沖，正好是產(chǎn)生99%完美奈奎斯特脈沖的所需的各種條件。
研 究人員們表示，對于光纖芯片制造商來說，設計一款能實現(xiàn)其編碼技術的發(fā)射器芯片，將會是更簡單明了的做法。其中應該要能包括“產(chǎn)生方形頻譜所需的調(diào)變器， 以及一組短延遲線與調(diào)變器，以產(chǎn)生數(shù)據(jù)序列，同時交錯于暫存序列中，以提高數(shù)據(jù)傳輸率，”Luc Thevenaz表示。
EPFL研究人員Camille Bres與Luc Thevenaz宣稱可使傳統(tǒng)光纖中的信息量提高10倍。
Source：EPFL3O3esmc
根據(jù)研究人員表示，由于這項頻譜合成技術能夠產(chǎn)生矩形的頻梳鎖相，因而也可能用于其他領域，包括微波光子學、光儲存以及全光采樣等。
本文授權編譯自EE Times，版權所有，謝絕轉(zhuǎn)載
編譯：Susan Hong
參考英文原文：Transmitter Chip Boosts Optical Fiber Capacity 10X，by R. Colin Johnson
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Transmitter Chip Boosts Optical Fiber Capacity 10X
R. Colin Johnson
PORTLAND, Ore. — Increase fiber optic capacity in existing networks by 10-times just by switching to a new kind of transmitter -- that's the claim of a research group at EPFL (école Polytechnique Fédérale de Lausanne, Switzerland). Using sinc-shaped Nyquist pulses, information can be encoded on pulses that overlap in the time domain and use a minimum of spectral bandwidth, thus maximizing optical capacity, according to the EPFL research team of Camille Brès and Luc Thévenaz.
Other groups have tried to produce Nyquist sinc pulses to minimize inter-symbol interference, but had to resort to complex signal generators. Brès and Thévenaz claim their spectral synthesis technique works better, plus is the only one that will be easy to implement for commercial optical transmitters.
"We synthesize a spectrum that gives the perfect pulse shape. We do it by using a simple intensity modulator to generate a set of spectral lines, regularly spaced and showing exactly the same amplitude and the same phase. This gives automatically in the time domain the sinc pulse shape," Thévenaz told us. "This is very simple and straightforward, but nobody thought to do it this way before."
Artists conception of Nyquist pulses encoding 10-times more information (Source: (C) Jamani Caillet / EPFL)
Artists conception of Nyquist pulses encoding 10-times more information (Source: ? Jamani Caillet / EPFL)
The EPFL team claims that in the lab a laser and a modulator -- to produce wide-spectrum pulses -- are all that's needed to generate Nyquist pulses that are 99 percent perfect.
The researchers claim that designing a transmitter chip that realizes their encoding technique should be a straightforward exercise for optical chipmakers, and would include "the modulators required to generate the square shaped spectrum and a set of short delay lines and modulators to generate data sequences and to interleave them in the temporal sequence, to increase the data rate," said Thévenaz.
EPFL research team of Luc Thevenaz and Camille Bres claim to pack 10-times as much information in conventional optical fibers. (Source: EPFL)
EPFL research team of Luc Thévenaz and Camille Brès claim to pack 10-times as much information in conventional optical fibers.
(Source: EPFL)
The spectral synthesis technique -- which produces a rectangular-shaped, phase-locked frequency comb -- could also be useful in other fields, according to the researchers, including microwave photonics, light storage, and all-optical sampling.
