Three dispersion compensation methods for
radio-over-fiber system
Tao Pu,* Fanqiu Meng, Jiyong Zhao, Tao Fang, Jilin Zheng, and Long Huang
PLA University of Science and Technology, College of Communications Engineering, Jiangsu 210007, China
Abstract. This paper introduces three different dispersion compensation methods based on superstructure fiber
Bragg grating (SSFBG) and an injection distributed feedback (DFB) laser. First, an SSFBG with a nonlinearity
group delay spectrum was designed to achieve tunable dispersion compensation. Second, an approach is pro-
posed for realizing single-sideband modulation with an optimum optical carrier to sideband ratio for maximizing
the transmission performance of a radio-over-fiber (RoF) system based on a strong optical injection-locked DFB
laser. Finally, a broadband chromatic dispersion compensation scheme using an optical phase conjugator based
on a DFB semiconductor laser is proposed and experimentally demonstrated in RoF links.
© 2015 Society of Photo-
Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.OE.55.3.XXXXXX]
Keywords: chromatic dispersion compensation; radio-over-fiber; nonlinearity chirped fiber Bragg grating; optical injection locking.
Paper 150982SS received Jul. 21, 2015; accepted for publication Sep. 9, 2015.
1 Introduction
Radio-over-fiber (RoF) technology has attracted great inter-
est recently in many microwave applications including cable
television, front/back haul for 4G/5G mobile wireless com-
munications, military radar, and radio telescopes.
1
In spite of
the advantages of the optical fiber and related technologies
such as low loss, high bandwidth, low weight, and immunity
to electromagnetic interference,
2
the chromatic dispersion
(CD) of the optical fiber deteriorates the performance of
the RoF by the spectrally periodical power fading.
1
To over-
come the CD-induced power fading, a number of approaches
have been proposed.
Automatic dispersion compensation for digital optical
communication systems was demonstrated, while no such
method has been proposed for the RoF system. Tunable
dispersion compensation was studied using nonlinearly
chirped FBGs for both single- and multichannel 40-Gb∕s
transmission system.
3
In Ref. 4, the dispersion of a 10 Gb∕
s-1000 km transmission line is successfully equalized in a
fully automatic manner.
Various methods have been proposed and demonstrated to
achieve single-sideband (SSB) modulation,
5–14
as the use of
SSB modulation can alleviate the power penalty induced by
dispersion. The SSB modulation can be obtained by filtering
out one of the sidebands,
5–7
using the SSB modulators,
8–10
and amplifying one of the sidebands.
11
Recently, approaches
were proposed to generate SSB modulation using injection-
locked semiconductor lasers.
12,13
In Ref. 12, the longer
wavelength of the modulated sidebands is resonantly ampli-
fied by the shif ted cavity mode of the injection-locked laser.
Also, the slave distributed feedback (DFB) laser is used as a
wavelength-selective modulator in Ref. 13. However, those
methods suffered from a low level of receiver sensitivity
originating from the large difference between the power of
the optical carrier and the modulated sideband.
6,14
In order to compare different chromatic dispersion
compensation (CDC) methods with their transmission per-
formance and deployment merits, we proposed three differ-
ent dispersion compensation methods for RoF systems based
on super structure fiber Bragg grating and an injection DFB
laser, respectively. The following sections of this paper will
discuss those three CDC methods, respectively. In Sec. 2,a
broadband CDC scheme using an optical phase conjugator
(OPC) based o n a DFB semiconductor laser is proposed and
experimentally demonstrated in RoF links. In Sec. 3, a super-
structure fiber Bragg grating with a nonlinearity group delay
spectrum was designed to achieve tunable dispersion com-
pensation. In Sec. 4, an approach to realize SSB modulation
with an optimum optical carrier sideband ratio (OCSR) for
maximizing the transmission performance of an RoF system
is demonstrated based on a strong optical injection-locked
DFB laser. Section 5 concludes this paper.
2 Optical Phase Conjugation in Injection
Distributed Feedback Lasers
First, we propose a midspan spectrum revised method for
static link applications. An optical phase conjugator (OPC)
based on a DFB semiconductor laser is placed in the midspan
of the link to compensate for the CD-induced power fading
in conventional DSB intensity-modulation-based RoF. The
DFB laser serves as a nonlinear medium to induce FWM
and provides a lasing beam as a pump light at the same
time.
15
Compared with the conventional OPC based on an
SOA or a DSF, no extra pump laser is required, leading to
a simpler and cheaper configuration. A broadband CD com-
pensation with a very wide 3-dB bandwidth up to 33 GHz is
achieved in the proposed RoF link with a fiber length
of 50.4 km.
The proposed experimental setup is shown in Fig. 1 .A
continuous light wave centered at 1552.38 nm with a power
of 13 dBm is launched into an IM with a 3-dB bandwidth of
40 GHz. To test the freque ncy response of the link, the IM is
*Author all correspond ence to: Tao Pu, E-mail: nj_putao@163.com 0091-3286/2015/$25.00 © 2015 SPIE
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Optical Engineering XXXXXX-1 March 2016
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Vol. 55(3)
Optical Engineering 55(3), XXXXXX (March 2016)
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