Switchable Brillouin frequency multiwavelength and
pulsed fiber laser
S. J. Tan
1,
*, H. Haris
2
, and S. W. Harun
2,3
1
School of Engineering, KDU University College, Utropolis Glenmarie, Shah Alam 40150, Malaysia
2
Department of Electrical Engineering, Faculty of Engineering, University of Malaya,
Kuala Lumpur 50603, Malaysia
3
Photonics Research Center, University of Malaya, Kuala Lumpur 50603, Malaysia
*Corresponding author: tsjin@yahoo.com
Received March 23, 2017; accepted June 6, 2017; posted online June 30, 2017
Switchable single and double Brillouin multiwavelength and pulsed laser is successfully demonstrated. Brillouin
spacing can be switched from single (0.08 nm) to double spacing (0.16 nm) or vice versa by swapping the ports of
the coupler in the proposed configuration. The proposed configuration can also be used to produce pulsed laser
by inserting a home-made carbon nanotubes saturable absorber into the laser cavity. The proposed system is
very versatile and flexible as it can be used as a multiwavelength laser or pulsed laser to cater for different types of
applications.
OCIS codes: 140.3500, 290.5900, 190.4370.
doi: 10.3788/COL201715.101401.
Multiwavelength fiber lasers are widely used in dense wave-
length division multiplexing (DWDM), optical sensing, and
spectroscopy
[1,2]
. Many approaches have been demonstrated
to produce multiwavelength sources, such as stimulated
Brillouin scattering (SBS)
[3]
, nonlinear polarization rotation
(NPR)
[4]
, four wave mixing (FWM)
[5]
, and spectral slicing
[6]
.
Among all these techniques, SBS is of interest and widely
used in the telecommunication industry due to its low
threshold power and narrow linewidth. SBS is a nonlinear
effect that arises from the interaction between the intense
pump light and acoustic waves in a nonlinear medium,
which results in the incident pump light to be back scat-
tered. This SBS effect can be cascaded and subsequently
generate multiple narrow Stokes lines with equal spacing.
Since the first demonstration of a hybrid Brillouin erbium
fiber laser (BEFL) by Cowle and Stepanov
[7]
, many efforts
have been put forward to generate a multiwavelength comb
with a constant spacing of 0.08 nm
[8,9]
.
Some works have also been carried out to double up
the channel spacing to 0.16 nm in order to facilitate the
de-multiplexing process. A double spacing multiwave-
length Brillouin fiber laser (DS-MWBFL) can be realized
using a four port circulator to extract out the even order
Stokes
[10]
. Recently, researchers paid much attention
to attain a switchable Brillouin spacin g fiber laser with
the purpose to provide a flexible multiwavelength
source in optical communication. A switchable spacing
MWBFL had been demonstrated by cascading Brillouin
nonlinear gain media and changing the Brillouin pump
(BP) power
[11,12]
. Moreover, the proposed setups in
Refs. [
11,12] are rather bulky, as they used two Brillouin
nonlinear gains in the range of 9–25 km long. Additionally,
Hu et al.
[13,14]
demonstrated a switchable spacing MWBFL
by rearranging the connection ports and using an optical
switch.
Apart from demonstrating the flexibility of switchable
Brillouin spacing, numerous researchers show interest and
are also investigating the dynamics of pulses generated by
SBS
[15–18]
. The occurrence of pulsation due to SBS is unsta-
ble, and this includes periodic, quasi-periodic and chaotic
oscillations. This instability is even more significant in a
MWBFL of long cavities. Cavity longitudinal modes with
different phases undergo gain competition and mode hop-
ping, resulting in the generation of unstable pulses. Pulse
stability can be enhanced by reducing the length Brillouin
gain medium (BGM). Nevertheless, stability of pulse is
still dependent on the phase relationship between the
BP and Stokes waves.
On the other hand, stable Q-switched and mode-locked
pulsed lasers have a broad range of applications from indus-
try to communication. A Q-switched laser, which delivers
high pulse energy, is widely used for surgery and micro-
machining, while a mode-locked laser with narrow pulse
width is used in optical transmission. There are numerous
ways to generate a pulsed fiber laser, and the incorporation
of a saturable absorber (SA) into the laser cavity is the
most popular method. Carbon nanotubes (CNTs) and gra-
phene SA are well known SAs and have been extensively
investigated in the past few years
[19,20]
. Newer SA materials
are subsequently discovered, such as a topological insulator
(TI)
[21]
and black phosphorus
[22]
.Furthermore,somere-
searchers incorporated a SA in a Brillouin laser cavity to
produce a Brillouin pulse
[23].
It would be great if a multiwavelength laser and stable
pulsed laser could be produced from a single laser cavity,
where its functionality can be switched between single and
double Brillouin spacing and a pulsed laser. Contrary to
the above mentioned techniques
[11,12]
, the Brillouin spacing
switching is realized by just swapping two ports of a cou-
pler, and the light propagation is still within the dual loop
COL 15(10), 101401(2017) CHINESE OPTICS LETTERS October 10, 2017
1671-7694/2017/101401(5) 101401-1 © 2017 Chinese Optics Letters
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