High Output Power Full Band Tunable Laser

High Output Power Full Band Tunable Laser

1.

INTRODUCTION

With the increase of transmission capacity in long haul
and metropolitan area due to fiber to the home (FTTH)
growth, data transmission rate per wavelength for wavelength division multiplexing (WDM) is migrating from 10
Gbps to 40 Gbps. With the implementation of 40 Gbps
transmission, new modulation formats using phase modulation such as differential phase shift keying (DPSK) anddifferential quadrature phase shift keying (DQPSK) arebecoming major. For further improvement in transmissioncharacteristics, signal return to zero (RZ) type RZ-DPSK
and RZ-DQPSK are applied. In modulation methods identified above, a multistage modulator is required. As a consequence, modulator insertion loss increases. In order tocompensate for the loss, high output power full band tunable laser is demanded than ever before.
Furukawa Electric has produced the full band tunable
laser diode module (FBT-LDM) with an optical output of
13 dBm. Moreover, Furukawa Electric commercializes
FBT-LDM with an optical output of 15 dBm, as shown inFigure 1 below. Table 1 shows the performance specification of the product. This commercialized FBT-LDM is moresuitable for modern 40 Gbps transmission.

Figure 1

2.

High output power full band tunable laser module.

FEATURE

Our FBT laser structure is shown in Figure 2. One semiconductor device contains an array of distributed feedback laser diodes (DFB-LD), where each DFB-LD has different oscillation wavelength, bent waveguide, optical
coupler and semiconductor optical amplifier (SOA). Thisstructure performance is superior in wavelength stability
and controllability because it is based on DFB laser technology which is already proven in optical communication
field. Also, because of a robust structure without mechanically moving part, it has excellent long term reliability.

DFB-LDarray

Bent
waveguide

Figure 2

Opticalcoupler

SOA

OpticaloutputStructure of FBT-LD.

In this device, the required optical output is obtained byamplifying output light from DFB-LD at SOA. Therefore, inorder to have high output at the FBT laser, it is significant
to increase the SOA gain. In general, SOA gain is limited
due to thermal roll-over and blue shift of gain-peak wavelength which are caused by injected carrier into active
layer, and the gain saturation caused by the increase ofphoton density in the active layer. The commercialized
high output FBT-LDM suppresses the blue shift by the
optimizing of the active layer structure. Also, by optimizing the waveguiding structure, the photon density isreduced and gain saturation is suppressed, which allows
us to attain high power output.
Figure 3 shows an example of FBT-LDM’s current-optical output-power characteristics. At the maximum 50°C,
more than 32 mW (15 dBm) of fiber facet output isattained even when any of DFB1 ~ 12 (from the shortest
wavelength to the longest wavelength) is driven.

3.

IN CONCLUSIONAs an optical source for 40 Gbps transmission, Furukawa
Electric succeeded in the development of a High Output
Power Full Band Tunable Laser with an optical output of15 dBm. This laser module is a product which can fulfill
very well clients’ demands in the current growth of the 40Gbps transmission system.
For more information, please contact
Global Business Solutions, Telecommunications Company
Tel: +81-3-3286-3253 Fax: +81-3-3286-3978

Furukawa Review, No. 38

20101High Output Power Full Band Tunable Laser

80

LD temp.=10℃

Fiber output power (mW)

70
60
5040
LD temp.=50℃
3020

DFB1
DFB7

100

DFB120

100

200

300

SOA current (mA)

Figure 3

Light-SOA current characteristics of high power FBTLDM. ( with DFB current = 150 mA )Table 2

Characteristics.
(Tc=25°C，BOL，unless otherwise specified)Parameters

Sym.

Optical output powerMin.

Pf

FRL15TCWC
LD operating temperature

TLDLD forward current

Typ.

Max.

IfLD

−−100,150

Conditions

mW

CW

50°C

Rated power, CW−mA

CW, dependent on channel
CW

3210Unit

LD forward voltage

VfLD

−−2.2

V

SOA forward current

IfSOA

−−525

mA

Rated power, CW

SOA forward voltage

VfSOA

−−

3.0

V

Rated power, CW

Wavelength

λp1528.773−

1563.863

nm

Rated power, CW

Spectral linewidth

Δv

−

−

10MHz

Rated power, CW

SMSR

40−−dB

Rated power, CWISO

25−−dBSide mode suppression ratio
Optical isolationRated power, CW
Rated power, CW

Relative intensity noise

RIN−−−135dB/Hz

Frequency stability to ITU gridΔfs−2.5−

2.5GHzFilter operating temperature

Tf

35−

50°C
GHz

OpRL<25 dB
100 MHz<f<10 GHz

Free spectral range

FSR−

50−

Capture range (negative side)

−CR

14−

22.5GHz

Capture range (positive side)

+CR

27.5−

36GHz

Rated power, CW

Power monitor current

Im40−1100µA

VrPD=5V, Rated power, CW

Power monitor dark current

Id−−100nA

VrPD=5V

Wavelength monitor current

Imλ40−

1100µA

VrPD=5V, Rated power, CW

Wavelength monitor dark current

Idλ−−100nA

Wavelength monitor current slope

Slope2−100µA/GHz

Tracking error

TE−0.5−0.5dB

Im=const., Tc=−5°C/35°C/75°C

TEC1 current (LD)

Itec1−−

1.4

A

Tc=75°C, Rated power, CW
Tc=75°C, Rated power, CW

VrPD=5V
VrPD=5V, See note 1

TEC1 voltage (LD)

Vtec1−−

2.4

V

TEC2 current (Filter)

Itec2−−

1.9

A

Tc=75°C, Rated power, CWTEC2 voltage (Filter)

Vtec2−−

3.0

V

Tc=75°C, Rated power, CW

Ptotal

−

4.0

4.5

W

Tc=75°C, Rated power, CWTotal power consumption(RLD+RSOA+RTECI+RTEC2)
Thermistor B constant

Bth−

3900

−

K

Thermistor resisitanceRth9.51010.5kΩ

TLD=25°C

Polarization extinction ratio

Er20−−dB

Rated power, CW

BOL (beginning of life), OpRL (optical return loss)

Furukawa Review, No. 3820102