Wavelength-Tunable and Bandwidth-Variable Ultra-Flat Optical Frequency Comb Block Generation From a Bismuth-Based Actively Mode-Locked Fiber Laser

Abstract

We generate, for the first time and to the best of our knowledge, a tunable ultraflat optical frequency comb (OFC) block from a 10-GHz bismuth-based actively modelocked fiber laser. A bismuth-based erbium-doped fiber (Bi-EDF) with a length of 1.5 m and a bismuth-based highly nonlinear fiber (Bi-HNLF) with a length of 4.1 m are used as a gain medium and a spectral broadening device, respectively. We also employ a wavelengthtunable and bandwidth-variable optical filter for an intracavity filter. The center wavelength of the OFC output can be widely tuned from 1535 to 1585 nm because the Bi-EDF has a broadband gain profile. A spectrally broadened ultra-flat OFC is successfully generated by the self-phase modulation in the Bi-HNLF. By tuning the filter bandwidth, the 10-dB spectral width and the pulsewidth of the generated OFC can be widely varied from 0.23 to 2.4 nm and from 3 to 20.1 ps, respectively. The fiber ring cavity is as short as 17.8 m. For the entire tuning ranges, the proposed bismuth-based tunable ultra-flat OFC generator also realizes stable bit-error-free mode-locking operation.

Flexible and Scalable Radio over Fiber Architecture

“…The flexibility of the introduced RoF system is demonstrated firstly at the optical wavelength generation through the use of an Optical Flat Comb Source (OFCS). This device generates optical carriers with tight optical channels (up to 12.5 GHz) rising the optical spectral efficiency [15], [16]. By assuming that each OFCS could generate 20 flat carriers, the C-band (1530-1565 nm) would be covered using 16 independent OFCS.…”

“…The proposed optical generation stage results in lower system implementation cost, lower power consumption, less overcrowding plant and better performance when compared to an equivalent design with multiple discrete lasers. Another key use for OFCS is the flexibility and the scalability aspect of the optical carrier source that settles the desired waveband by adjusting the wavelength of the CW laser and fixes optical carriers number and interspace by handling voltage levels at the Mach Zehnder modulator arms [16]. Thus, the proposed optical wavelengths source is scalable and fits the networks optical resource needs by adjusting the OFCS parameters.…”

Avaliação experimental da estabilidade de pentes ópticos de frequência gerados por laço de recirculação com amplificador óptico a semicondutor e circuito optoeletrônico de realimentação dedicado

“…Na sequência, a título de ilustração, a estabilidade do sistema foi investigada para um filtro passa-baixa de primeira ordem e com uma constante de tempo. Este filtro é utilizado, por exemplo, na implementação de PLLs de primeira ordem modificada[32][33]. O objetivo é criar diretrizes que permitam o projeto do circuito A&F, que será retomado no Capítulo 5.…”