Performance Analysis of 1310/1490 Nm Demultiplexer based on

Multimode Interference Coupler for PON

Devendra Chack, V. Kumar and Dev Prakash Singh

Department of Electronics Engineering, Indian School of Mines, Dhanbad, 826004, India

Keywords: Multimode Interference Coupler, Demultiplexer, Passive Optical Network.

Abstract: The design and analysis of a 1310/1490-nm demultiplexer based on Multimode Interference (MMI) coupler

for Passive Optical Networks (PON) has been studied in this paper. Numerical simulations with finite

difference Beam Propagation Method (BPM) have been utilized to optimize the operation of the proposed

demultiplexer. The device has been designed with optimized width and MMI length and its analysis has been

done based on extinction ratio and Insertion loss. Restricted interference has been used to reduce the size of

the device. The device has been solely designed using 1310 nm as upstream and 1490 nm as downstream of

data for Passive Optical Network communication system.

1 INTRODUCTION

Fiber-to-the-home Passive Optical Networks are one

of the evolving telecommunication networks that uses

wavelength multiplexing/demultiplexing to have

point to multipoint fibers to the end points. They are

used for ultra-high speed internet communication for

home entertainment and industrial demands (

Fan et

al., 2009

). Few standards, which were earlier used are

Broadband Passive Optical Networks (BPONs) set by

ITU and Ethernet Passive Optical Networks (EPONs)

set by IEEE and are based on time division

multiplexing. A currently widely used standard is

Gigabit Passive Optical Networks (GPON) set by

ITU, which uses three wavelength channels for

multiple applications including 1310 nm for upstream

of data with a bit rate of 1.25 Gb/s, 1490 nm for

downloading of voice and data with a bit rate of 2.5

Gb/s and 1550 nm is reserved for video broadcasting

(Cale

et al., 2007; Filka, 2010). Video service of PON

could be upgraded to digital form of signal using

internet protocol television (IPTV) but the

transmission type is unicast (FOA 2014; Horvath et

al., 2015). This negates the need of separate

wavelength for video and same wavelength can be

used for downloading video ie.1490 nm in case of IP

Protocol.

Devices based on multimode interference support

large number of modes due to which there has been a

growing interest in its application and effects in the

field of integrated optics (Soldano and Pennings,

1995). MMI based demultiplexers have attracted

much attention because of its compact size, low loss,

larger fabrication tolerances and the broad bandwidth

properties and hence they are increasingly used for

wavelength demultiplexing (Chack et al., 2015; 2014;

Jerabek et al., 2013; Shi et al., 2007; Paiam et al.,

1995). This paper presents a simple design of a

demultiplexer to separate wavelengths 1310 nm and

1490 nm at two different ports such that it can be used

by a GPON system for uploading and downloading.

The device length and width have been optimized

with the help of Beam propagation method based

simulations.

2 DEVICE DESIGN AND

ANALYSIS

A multimode section supporting many modes

reproduces input field profile in single or multiple

images at periodic intervals along the direction of

propagation of the guide and it is called as” Self-

imaging” (Soldano and Pennings, 1995). Using the

concept of self-imaging, we have designed our device

with material InGaAsP as core layer of waveguide

and InP as cladding layer (

Adachi and Sadao, 1982;

Chack et al., 2015). InP-based optical power splitters

are of great advantage to photonic integration in 1550

nm optical communication systems compared with

Chack, D., Kumar, V. and Singh, D.

Performance Analysis of 1310/1490 Nm Demultiplexer based on Multimode Interference Coupler for PON.

DOI: 10.5220/0005649502230226

In Proceedings of the 4th International Conference on Photonics, Optics and Laser Technology (PHOTOPTICS 2016), pages 225-228

ISBN: 978-989-758-174-8

225

other material, such as AlGaAs/GaAs and SOI (Li et

al., 2011). As an experimental design, we have taken

these materials for analysis at 1310 nm and 1490 nm

to have high optical power operation. In this work, we

have chosen the simulation parameters given below

in Table 1. The theory and properties of MMI devices

has been described below. Beat length (L

) for a

multimode section of waveguide is defined as

= π/ (β

- β

), (1)

where β

and β

are the propagation constants of

fundamental and first order modes, respectively

(Paiam et al. 1995). In order to reduce device size,

restricted interference has been used in which modes

2,5,8…are not excited in multimode waveguide. In

restricted resonance mechanism at MMI length of

MMI

= k.L

, a direct or mirrored image of the input

field is formed if n is an even or odd integer,

respectively. The MMI width is adjusted to satisfy the

total length of MMI region as

MMI

= n. L

(1310) = (n +1). L

(1490) (2)

where n is an integer.

Further, if the MMI section of the device satisfies

the relation in Eq. 2, the wavelengths 1310 nm and

1490 nm can be successfully separated by choosing a

suitable width and length of MMI section

. The width

of the MMI section

is chosen using the ratio of beat

lengths at 1310 nm and 1490 nm for transverse

electric polarization. The beat length ratio, which

corresponds to the ratio of two integers is generally

taken and width corresponding to that ratio is chosen.

Figure 1 shows that beat length ratio corresponding to

width 3.4 µm is 1.1 and hence integer n is taken as 10

and (n+1) =11 so that (n+1)/n=1.10.

Now from Eq. 2, we have L

1310

1490

=n/n+1

which results in L

MMI

= 10L

1310

= 11L

1490

. For TE

polarization, the calculated value of L for 1310 nm

and 1490 nm are 50.32 µm and 45.84 µm respectively

at width of 3.4 µm. Hence L

MMI

for 1310 nm and 1490

nm are 503.20 µm and 504.21 µm respectively.

Figure 2 clearly depicts the structure of the

proposed demultiplexer where the width of the MMI

section has been optimized at 3.4 µm. The width of

input and output waveguides has been taken to be 0.8

µm. Initially input and output waveguides are taken

at a lateral shift of around W

MMI

/3. Input waveguide

is at an offset of 1.1 µm. Two output waveguides are

separated by distance 1.4 µm. The complete structure

has been first optimized at MMI length of 449 µm.

The designed device is shorter in length in

compression the existing similar device with tapered

geometry (Chang et al., 2010).

Table 1: Parameter for demultilpexer MMI structure.

Parameter Value

Guide Refractive index 3.290

Cladding Refractive

index

3.167

I/O waveguide width 0.8 μm

1490 nm

1310 nm

MMI width 3.4 μm

MMI length 449 μm

Polarization TE

BPM Solver Paraxial

Engine Finite Difference

Boundary Condition TBC

Figure 1: Calculated beat length ratio (L

1310

1490

) as a

function of MMI width for TE polarization.

1490nm 1490 nm

Port 1 Port 2

1310 nm 3.4 µm

Port 3

1310 nm

Figure 2: Schematic diagram of the proposed

demultiplexer.

3 RESULTS AND DISCUSSTION

From Fig. 3, it can be observed that wavelength 1310

nm is obtained at port 3 with highest optical intensity

while wavelength 1490 nm is obtained at port 2 with

highest optical intensity at MMI length of 449µm for

PHOTOPTICS 2016 - 4th International Conference on Photonics, Optics and Laser Technology

226

separation distance between output waveguides to be

1.4 µm and input lateral offset as 1.1 µm. Further, to

measure the performance of device, Extinction Ratio

and Insertion Loss has been calculated using the

relations:

Extinction Ratio = 10 log (P

/ P

)

(3)

Insertion Loss = -10 log (P

) (4)

where P

is the power from desirable output

waveguide, P

is the power in input waveguide and P

is the power from undesirable output waveguide (Shi

et al., 2007). From fig. 4, it is clear that optimized

length is 449 µm.

Figure 3: Normalized field distribution versus MMI Length

for λ=1310 nm and 1490 nm wavelength for TE

polarization.

Two dimensional simulations of field distribution

for TE polarization can be seen in Fig. 5, where 1490

nm get separated at port 2 and 1310 nm at port 3. We

have also optimized the output by varying the gap size

between output waveguides and simultaneously

changing the corresponding lateral offset of input

waveguide. From fig. 6, we can observe that the

output has been optimized at a gap size of 1.3 µm or

a lateral shift of 1.05 µm.

Table. 2 and Fig. 6 show that the insertion loss for

both the wavelengths is below 1dB and and extinction

ratio for 1310 nm and 1490 nm are around 17 dB and

20dB at optimized MMI length of 449 µm. TM beat

lengths were also calculated but the optimized MMI

length was different as compared to its TE

counterpart. For TM mode, optimized MMI length

was found to be 440µm. This shows that optimum

value for both polarizatios are different and hence we

have optimized our designed demultiplexer only for

TE polarization.

Table 2: Output Powers (normalized to input power) of two

output ports of the proposed demultiplexer at two

wavelengths.

Wavelength

(nm)

Extinction

Ratio

(dB)

Insertion

Loss

(dB)

1310 16.93 0.924

1490 20.17 0.546

Figure 4: Simulation performance for TE mode as a

function of MMI length.

Figure 5: 2-D simulations of the field distribution (a) port 2

for wavelength 1490 nm and (b) port 3 for wavelength 1310

nm.

Performance Analysis of 1310/1490 Nm Demultiplexer based on Multimode Interference Coupler for PON

227

Figure 6: Simulation performance for TE mode as a

function of branching separation distance (Gap size)

between output waveguides.

4 CONCLUSIONS

A 1310/1490 nm wavelength demultiplexer has been

proposed based on conventional MMI structure. It has

been shown that separation distance between output

waveguides and the lateral offset of input waveguide

affect the simulation output and we optimized the

branching separation distance at 1.3 μm to achieve

maximum output optical field for demultiplexer. The

present simulation based on finite difference beam

propagation shows that the proposed demultiplexer

has good performances such as a low insertion loss

and a high extinction ratio at 1310 nm wavelength,

which has been found to be IL= 0.924 dB and

extinction ratio = 16.93 dB, respectively, and at 1490

nm wavelength, IL= 0.546 dB and extinction ratio =

20.17 dB, respectively, for quasi-transverse-electric

(quasi-TE) polarization. The 1310/1490 nm

wavelength demultiplexer may be an important key

component in application of Passive Optical Network

communication system in near future.

REFERENCES

Fan, S.H., Guidotti, D., Chien, H.C. and Chang, G.K., 2009,

May. A novel compact polymeric wavelength

triplexer designed for 10Gb/s TDM-PON based on

cascaded-step-size multimode interference. In

Electronic Components and Technology Conference,

2009. ECTC 2009. 59th (pp. 220-223). IEEE.

Cale, I., Salihovic, A. and Ivekovic, M., 2007, June. Gigabit

passive optical network-GPON. In Information

Technology Interfaces, 2007. ITI 2007. 29th

International Conference on (pp. 679-684). IEEE.

FILKA, M., 2009. Optoelectronics: for telecommunications

and informatics. Brno, ISBN 978-0- 615-33185-0,

pp.978-80.

The Fiber Optic Association, Inc, 2010-2014 “Fiber Optic

Network Optical Wavelength Transmission Bands”,

Guide to Fiber Optics and Premises cabling,

http://www.thefoa.org/tech/ref/basic/SMbands.html.

Horváth, T., Kočí, L., Jurčík, M. and Filka, M., 2015.

Coexistence GPON, NG-PON, and CATV systems. ,

International Journal of Engineering Trends and

Technology Volume 21, pp. 61-66.

Soldano, L.B. and Pennings, E., 1995. Optical multi-mode

interference devices based on self-imaging: principles

and applications. Lightwave Technology, Journal of,

13(4), pp.615-627.

Chack, D., Kumar, V. and Raghuwanshi, S.K., 2015.

Design and performance analysis of InP/InGaAsP-

MMI based 1310/1550-nm wavelength division

demultiplexer with tapered waveguide geometry. Opto-

Electronics Review, 23(4), pp.271-277.

Chack, D., Agrawal, N. and Raghuwanshi, S.K., 2014. To

analyse the performance of tapered and MMI assisted

splitter on the basis of geographical parameters. Optik-

International Journal for Light and Electron Optics,

125(11), pp.2568-2571.

Jerabek, V., Busek, K., Prajzler, V., Mares, D. and

Svoboda, R., 2013. The design of polymer planar

optical triplexer with MMI filter and directional

coupler. Radioengineering, 22(4).

Shi, Y., Anand, S. and He, S., 2007. A polarization-

insensitive 1310/1550-nm demultiplexer based on

sandwiched multimode interference waveguides.

Photonics Technology Letters, IEEE, 19(22), pp.1789-

1791.

Paiam, M.R., Janz, C.F., MacDonald, R.I. and Broughton,

J.N., 1995. Compact planar 980/1550-nm wavelength

multi/demultiplexer based on multimode interference.

Photonics Technology Letters, IEEE, 7(10), pp.1180-

1182.

Li, M., Zhang, C., Zhu, H. and Chen, M., 2011, November.

Design and fabrication of a 1-by-4 multimode

interference splitter based on InP. In SPIE/OSA/IEEE

Asia Communications and Photonics (pp. 83072M-

83072M). International Society for Optics and

Photonics.

Adachi and Sadao,”Refractive indices of III–V compounds,

1982: Key properties of InGaAsP relevant to device

design”, J. Appl. Phys. 53, 5863–5869.

Chang, H.H., Kuo, Y.H., Jones, R., Barkai, A. and Bowers,

J.E., 2010. Integrated hybrid silicon triplexer. Optics

express, 18(23), pp.23891-23899.

PHOTOPTICS 2016 - 4th International Conference on Photonics, Optics and Laser Technology

228