CUBE-ER100

Polarization Extinction Ratio Meter

The CUBE-ER100 is a rotating polarizer-based polarization extinction ratio (PER) meter for fiber & free-space optical applications.

Because of its compact size & fast measurement speed up to 50 points per second, it can easily be integrated into PM fiber auto-alignment systems.

Features

High PER (>52dB)
Works for DFB and ITLA laser
One unit covers 600nm~1600nm
Accessories for Fiber Array, MPO and Collimators
PER Meas. of Free-space Light Source
Works for High Power Laser

Description

It has one full-speed USB 2.0 port for remote control, one UART port for interconnection between different CUBEs, two analog outputs for the closed-loop control of PM fiber auto-alignment system, and two general-purpose TTL input/output for measurement and control synchronization. CUBE-ER100 can work with polarization maximizer cube CUBE-PM100 to perform fast and accurate PER and angle measurements of PM fiber spools, coils, and components without splicing the inline polarizer and PM connectors.

CUBE-ER100 module has an FC adapter as the default input; other input accessories are available for SC and LC connectors, PM collimators, fiber arrays, PIC chips, free-space parallel beam, and free-space point sources. CUBE-ER100 modules can also be stacked to simultaneously measure multiple outputs of PM coupler, PM splitter, Lithium Niobate IOCs, etc.

CUBE-ER100 Specifications

Operating Wavelength Range

600~1600 nm

Calibration Wavelength

630, 850, 980, 1060, 1310, 1550 nm

PER Range @ 1310 or 1550 nm

0~52dB for input power -5 to 11dBm @1550nm

0~50dB for input power -5 to 11dBm @1310nm

0~40dB for input power -20 to -5dBm

0~30dB for input power -30 to -20dBm

PER Range @ 630, 980, or 1060 nm

0~40dB for input power -5 to 11dBm

0~35dB for input power -15 to -5dBm

Input Adapters

FC/LC/SC optical fiber adapters

Free-space beam adapter

Fiber array adapter

Optical Power Range

-65~11dBm @ 1310/1550nm

PER Resolution

0.05 dB

Angular Resolution

0.028°

PER Accuracy

0.05 dB+PER*0.7%

Absolute Angular Accuracy

1°

Angular Repeatability

±0.06°

Optical Power Measurement Accuracy

±0.5 dB

Optical Power Resolution

0.02 dB

Measurement Rate

Up to 10 measurements per sec for normal mode

Up to 50 measurements per sec in tracking mode

Measurement Mode

Continuous, tracking, and manual mode

Operating Temperature

0~40 °C

Display

2.42" 128x64 OLED graphic display

Electrical Power Supply

DC 15V / 1A

Communication Interface

USB and UART

GPIO

DB9 connector including two analog outputs, two TTL input/output triggers

Dimensions

63.5 x 63.5 x 85 mm

Notes:

Specifications are given at 23 ± 5°C
FC/PC connector with narrow key

3. The power range can be extended to 14dBm~-69dBm, and wavelength range can be 800nm~1650nm, please contact info@inlinephotonics.com to get more information.

CUBE-ER100 Drawings

Polarization Extinction Ratio Cube:

Request Quotation

CUBE-ER100-XX-X-X

6— 600~1600nm

S — Standard mode

E — Extended power range: 14 ~ -69 dBm

C — Customized Model

Connector Type — FC, SC, LC

Accessories:

CUBE-ER100-A-XXX

L40 — Lens assembly for free-space beam (f=40mm)

FA — 1D fiber array adapter for the fiber array with

width of 1~5mm

COL — Collimator holder

FAH — Fiber array holder

MTP— MTP or MPO connector

10A — High power attenuator (10dB)

20A — High power attenuator (20dB)

LC — LC optical input adapter

SC — SC optical input adapter

FC — FC optical input adapter

IC — Communication cable between

Calibration Standards:

CUBE-ER100-S-XXX

AFC — Angle artifact for FC input adapter

ALC — Angle artifact for LC input adapter

ASC — Angle artifact for SC input adapter

ER — ER artifact with ER>50dB @1550nm

1. PER Measurement of Components with PM pigtails

4. PER Measurement of Fiber Array/MTP

2. PER Measurement of Waveguide Chip

5. PER Measurement of DFB or ITLA Laser

3. PER Measurement of High Power Laser

6. AUTO Alignment of Devices with PM Fiber

PM Pigtailed Components

To obtain fast and accurate results, use CUBE-PM100 to replace the inline polarizer and PM fusion splicer.

Waveguide Chip

User can adjust the lateral position of the lens and distance from the lens to the waveguide output to maximize the power reading of the CUBE-ER100.

High Power Laser

Attenuator can be a neutral-density filter (NDF) or partially reflective mirrors.

PM Fiber Array

Fiber array is installed on an xy-translation stage which adjusts the position of the channel under test to the center of the lens.

PM MTP/MPO Connector

MTP/MPO is installed on an xy-translation stage which adjusts the position of the channel under test to the center of the lens.

DFB or ITLA Laser

(stretching fiber)

CUBE-ER100 measures the ellipticity and orientation of the output elliptical polarization under different tensions. A software will calculate the corresponding PER by least squares method. Click here for details.

DFB or ITLA Laser

(heating fiber)

CUBE-ER100 measures the ellipticity and orientation of the output elliptical polarization under different tensions along the PM fiber. A software calculates the corresponding PER by least squares method. Click here for details.

PM Fiber Auto Alignment

CUBE-ER100 converts PER, optical power, and angle to analog signals for the automation system.

Operation Principle

DOWNLOAD

Cube-ER100 Operation Principle.pdf

1. Polarization Extinction Ratio of PM Fiber

When a beam of light transmits in polarization-maintaining (PM) fiber, the light can be considered as a superposition of two orthogonal linearly polarized lights, one is polarized along the slow axis of the PM fiber, and another is along the fast axis. When the PM fiber is moved or bent within its specified range, the optical power of these two polarization components is theoretically conserved. However, crosstalk between these two polarization components can occur when an external mechanical force or thermal expansion of different materials introduces transverse stress on the fiber. The optical power ratio of these two polarization components at the output of PM fiber is called the polarization extinction ratio (PER), which is represented by the following formula:

(1)

2. PER Measurement Using Broadband Laser Sources

As we know, PM fibers have a large birefringence, which introduces an optical path difference Dl between two orthogonal linear polarization components polarized along the slow and fast axes. The Dl can be calculated according to the length l and beat length l_beat of the PM fiber as follows:

(2)

where l is the central wavelength of the light source. If the coherent length of the light source is shorter than the optical path length difference, these two polarization components are incoherent at the PM output, and the optical power after the rotating polarizer can be simplified as:

(3)

where α is the angle between the slow-axis and the transmission axis of the polarizer. From Eq. (2), one can find

(4a)

(4b)

(4c)

Substituting Eqs. (4) into Eq.(2) , one can rewrite the PER as:

(5)

Thus, the PER measurement is simplified to measure the ratio between the maximum and minimum power during polarizer rotation.

3. Minimum bandwidth of the broadband Light Source Used for PER Measurement

As we discussed above, the coherent length Lc of the light source should be shorter than the optical path length difference Dl introduced by the PM fiber. Lc can be estimated by:

(6)

where l is the center wavelength of the light source and Dl is the corresponding 3dB spectral linewidth.. Substituting Eqs. (2) and (6) into the relationship Dl>Lc , one can find

(7)

For convenience, we list the typical coherent length of the light source vs. linewidth in Table 1 and the required minimum linewidth of the light source vs. beat length in Table 2.

4. PER Measurement of Narrow-band DFB or ITLA Lasers Using CUBE-ER100

The PER measurement using a conventional rotating polarizer method requires a broadband light source with short coherent length. However, in some applications, such as coupling light from a narrow bandwidth DFB or ITLA laser into a PM fiber pigtail, as shown in Figure 2, one doesn’t have the option of using a short coherent length light source. Generally, the coherent length of a DFB laser or ITLA laser is over tens of meters, which is much longer than the optical path difference between the slow and fast axes of PM fiber (see Table 2). In this condition, the polarization state at PM output is an ellipse, which depends not only on the power ratio between two orthogonal linear polarization states along the slow and fast axes but also on their relative phase. The ratio of the maximum to the minimum powers measured by the rotating polarizer method is the ellipticity of the polarization ellipse, which is not equal to the ratio of the optical power of the two polarization components polarized along the slow and fast axes. The angle corresponding to the maximum power is generally not in the direction of the slow or fast axis.

The phase difference d between the slow and fast axis is related by the length l of the PM fiber and the birefringence Dn of the PM fiber as follows:

(8)

where l is the central wavelength of the light source. d changes when PM fiber is heated or stretched because heating or stretching fiber causes changes in Dn and l. Therefore, during heating and stretching the fiber, the ellipticity and orientation of the output polarization will change, and the corresponding SOP will draw a circle on the Poincare Sphere. CUBE-ER100 provides computer software to calculate the circle's radius R by fitting the ellipticity and angle curves shown in Figure 3. From the calculated R, the PER of DFB or ITLA laser can be deduced by

(9)

Waveguide

High Power

broadband

Device

Fiber Array

MTP/MPO

DFB and ITLA

Auto Alignmet