Description
The COH24 is a single polarization 90° optical hybrid that enables to extract phase and amplitude from a single polarization signal by performing four 90° phase stepped interferences between the signal and a LocalOscillator (LO). The COH24-X is a new generation optical hybrid with improved performances (among other things, a wider operating wavelength range and much better dual uniformities).
The COH28 and COH28-X are based on two single polarization 90° optical hybrids that enable to extract phase, amplitude and polarization from a signal with any polarization.
These products are purely passive and athermal.
The COH24-X and COH28-X also feature a phase tunability option in order to perfectly adjust the 90° of the hybrid depending on the wavelength used.
Kylia also offers a dual polarization 180° hybrid named COH22.
Block diagram
Below is a block diagram showing how the four 90° phase stepped. Interferences are done in the optical hybrid.
Absolute maximum ratings
Parameter
Symbol
Min
Typ.
Max
Unit
Remarks/Conditions
Maximal optical input power
OpIn
300
mW
Storage temperature range
STR
-40
80
°C
Humidity
RH
5
85
%
Non condensing
Fiber bend radius
20
mm
Maximal input voltage1
U
4
V
1 for phase tunability option only (COH24-X and COH28-X)
Operating conditions
Parameter
Symbol
Min
Typ.
Max
Unit
Remarks/Conditions
Operating wavelength
COH
OWR
1520
1570
nm
COH-X
1520
1625
Operating temperature range
OTR
0
70
°C
Specifications
Parameter
Symbol
Min
Typ.
Max
Unit
Remarks/Conditions
Insertion Losses
from Signal2
COH24/COH24-X
IL→S
7.0
8.5
dB
Including 6dB of natural losses
COH28/COH28-X
7.0
8.5
Including 6dB of natural losses
Insertion Losses
from LO2
COH24/COH24-X
IL→LO
7.0
8.5
dB
Including 6dB of natural losses
COH28/COH28-X
10.0
11.5
Including 9dB of natural losses
IL uniformity2,3
COH
ΔIL
1.0
2.0
dB
Without connectors
COH-X
0.5
1.0
IL dual
uniformity2,3
COH
Δdual
0.5
1.0
dB
Between balanced outputs
Without connectors
COH-X
0.2
0.5
Phase shift between I and Q2
φ
85
95
deg
Skew4
0.5
1
ps
Measured at connectors end
Optical return loss
ORL
35
dB
Polarization splitting ratio5
PSR
20
dB
Separation of X and Y
polarization at the Signal input by the PBS
Phase shift tunability2,6
Δφ
+/-20
deg
For a 3V voltage
Packaging size7
COH
70 x 52 x 10
mm3
COH-X
180 x 32 x 19.5
Fiber Pigtail Type
SM
SMF-28
With 900µm loose tube
PM
PANDA PM
Fiber Pigtail Length
0.9
1.0
1.1
m
Other lengths on request
2 measured over OTR and OWR for all states of polarization
3 from Signal or LO
4 for all outputs
5 for COH28 and COH28-X only
6 for phase tunability option only
7 excluding fiber boots
COH-X and COH dual uniformities
The graphs above compare the dual uniformities, a key parameter of 90° optical hybrids, for the Signal and LO of a standard hybrid (COH) and a new generation one (COH-X). We can clearly see that COH-X exhibitsmuch better dual uniformities over a wider range.
Phase tuning option
The 90° phase shift of the hybrids depends slightly on the wavelength. For example, it increases of about 2° to 3° over the C-band. That means that if at 191THz the phase shift is 88.5° it will be approximately 91.5° at 197THz (see next paragraph for some typical measurements).
For some applications it can be useful to have a very precise 90° phase shift whatever the wavelength you are working at. That is what the phase tunability option on COH-X enables. With this option, two voltages (V1 and V2) between 0V and 4V can be applied on the hybrid. One will increase the phase shift when thesecond one will decrease it. Hence for any wavelength in the OWR the phase shift can be adjusted to beprecisely equal to 90°.
Below are the packaging of a COH24-X with the phase tuning option and a typical measurement of the phase shift versus voltage for a COH24-X device:
Typical measurements
The two following diagrams show the typical behavior of the 90° phase shift. On the first one, one can see that the variation of the phase shift versus the temperature is very small (less than 1°). Hence the hybrid does not need any temperature control to ensure a precise, stable 90° phase shift. On the second diagram, one can see that the variation of the phase shift versus the wavelength is small (less than 3°). However if for some particular application one need to have a very precise 90° phase shift, the phase tunability option available on COH-X will enable to adjust it precisely for any wavelength of the OWR.
The third diagram shows the IL variations versus the temperature. One can see that each output do not have exactly the same variation but they all remain small, as well as dual and total uniformities.
Application note: full tunable 90° hybrid
In order to have the possibility to control all the parameter of a COH24-X or a COH28-X, we propose in a 19inches-2U rack a system where the user can adjust:
- the phase
- the insertion losses uniformity
- the skew
Dual-Polarization 180° hybrid
Kylia offers a dual-polarization 180° hybrid based on the following block diagram and specifications:
Parameter
Symbol
Min
Typ.
Max
Unit
Remarks/Conditions
Insertion Losses from Signal1
IL→S
4.0
5.0
dB
Including 3dB of natural losses
Insertion Losses from LO1
IL→LO
7.0
8.0
dB
Including 6dB of natural losses
IL uniformity1,2
ΔIL
0.8
1.5
dB
Without connectors
IL dual uniformity1,2
Δdual
0.2
0.8
dB
Between balanced outputs Without connectors
Phase shift between I and Q1
φ
85
95
deg
Skew3
0.5
1
ps
Measured at connectors end
Optical return loss
ORL
35
dB
Packaging size4
70 x 52 x 10
mm3
Fiber Pigtail Type
SM
SMF-28
With 900µm loose tube
PM
PANDA PM
Fiber Pigtail Length
0.9
1.0
1.1
m
Other lengths on request
1 measured over OTR and OWR for all states of polarization
2 from Signal or LO
3 for all outputs
4 excluding fiber boots
Fiber type and connectors
For the single polarization hybrids (COH24 and COH24-X) both the Signal and Local Oscillator have PM fiber. The outputs have SM fiber.
For the dual polarization hybrids (COH22, COH28 and COH28-X), the Local Oscillator has PM fiber and the Signal has SM fiber. The outputs have SM fiber.
For all of these products, the outputs can optionally have PM fiber with a PER of 20dB.
For COH22, COH28 and COH28-X, the Signal input can optionally have a PM fiber aligned such that the slow and fast axes are split by the input PBS. Eventually the fiber can be aligned in a different way upon customer request.
The devices can be proposed with any kind of connectors (FP/UPC, FC/APC, SC/PC, SC/APC, LC/PC, E2000/PC, E2000/APC).
All our COH products are offers with 1m fiber lengths. Other fiber lengths, down to 10cm are available on request
Wavelength range
Both COH-X can be proposed at different wavelength range, from the visible to the IR. The device will be operational on a wavelength range of a tens of nanometers centered on the wavelength required by customer. Products at 1300nm, 1064nm and 800nm have already successfully been manufactured.
Splitting ratio
For a standard COH we have 50% of the optical power from SIGNAL (or LO) on I and 50% on Q. This splitting ratio can be customized. For instance, we can split the optical power from SIGNAL (or LO) in order to have 10% on I and 90% on Q. Splitting ratio of SIGNAL and LO can be different.
Custom product
Thanks to our free-space technology we can easily customize most of our product and so it is for the 90° optical hybrids. Customer can feel free to ask for any customization they need. We will examine the request and do our best to have a positive answer.
Package layout
描述 [描述] 单偏振90°光混合,通过在信号和本地振荡器(LO)之间执行4次90°相位步进干涉,可以从单偏振信号中提取相位和幅度。