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Variable Optical Attenuator (Statistical) - Lumfoundry Template

A statistically enabled variable optical attenuator model.  This device is assumed to be composed of an active region in the middle, connected to the input/output ports by passive transitions and waveguides. For a diagram of the expected layout, see the Internal Model Diagram in photonic model page. 

The statistical parameters are delta_width, delta_height, delta_ridge_height, delta_Attn_eff, and delta_IL. 

For more information on statistical CMLs, see Statistical CMLs. 

Note: For legacy data format (2022 R2.4 and older) please visit following link:

Variable Optical Attenuator (Statistical) - Lumfoundry Template (Legacy)

Template: voa_stat_te_c

Photonic Model: phase_shifter_electrical

Quality Assurance Test: phase_shifter_electrical QA

Statistically Enabled Parameters: neff (active wg), ng (active wg), Attn_eff, IL

Supported Parameters: length of the active region.

Interoperability with Cadence Virtuoso:

  • Circuit design flows using INTERCONNECT model: Yes.
  • Circuit design flow using photonic Verilog-A model: Yes.

Modeling Data

The source data template for a Variable Optical Attenuator can divided into two sections.

  1. For new users (continue with the following section: Basic Data Requirement)
  2. For advanced users (continue with section: Complete Data Requirement)

In order to get started and add a custom variable optical attenuator element into the compact model library (CML), a user only needs to edit the data listed in the ‘basic data requirement section’ below, while all other data (i.e. the advanced element data) can be left as is.

Note: Advanced users please jump start with Complete Data Requirement (for advanced users) section.

Basic data requirement section (for new users)

The basic or minimum data required to build the variable optical attenuator model is described below.

general

"general" is a struct with following fields:

Field Type Description
description string A string containing a brief description of the model, which will be displayed to the end user.
notes cell

A cell array providing model notes which will be displayed to the end user. Each element of the cell is a struct with the fields:

  • property: String with the name of the note.
  • value: String with the contents of the note.

ports

"ports" is a struct with following fields:

Field Type Description

opt_1

 struct with fields described in table below Port definition corresponding to the optical ports

opt_2

ele_an

 Port definition corresponding to the electrical cathode and anode

ele_cat

Each struct above consists of following fields:

Field Type Description
name string The name of the port, which will be visible to the end user. This name should be consistent with the name that will be used for netlisting.
dir string The directionality of the port, either "Input", "Output", or "Bidirectional"
pos string

The side of the model which the port will be displayed on, either "Left", "Right", "Top", or "Bottom"
order number

The order in which the port is listed in a netlist.

parameters

"parameters" is a struct with following fields:

Field Type Description
wg_length
 struct with fields described in table below

The length of the active waveguide region.

Each struct above consists of following fields:

Field Type Description

default

number

The nominal value of the parameter in SI unit.
min

number

Minimum allowed value if the visible_to_user is set to True.
max

number

Maximum allowed value if the visible_to_user is set to True.

model_data

"model_data" is a struct with following fields:

Field Type Description

mode_data

cell

M x 1 cell array where M is the number of modes. Each element of the cell is a struct with fields:

  • name: string with the name of the mode ("TE" or "TM")
  • ID: integer to identify the mode, which should be 1 for "TE" and 2 for "TM". These should be consistent across the entire CML.

Note: This model only supports up to two modes.
IV_data

struct

The current data, as a function of voltage and temperature, in the form of a struct with the following fields:

  • voltage: Vx1 matrix containing the voltage (V) data at which the current values have been provided.
  • current: Vx1 matrix containing the current (A) data corresponding to voltage points.

Note: At least two bias points must be provided.

FOMs

"FOMs" is a struct with fields below. This data is required for CML Compiler to run quality-assurance tests on the final model. It is also optionally used by CML Compiler to fine-tune the internal model to provide the expected behavior.

If the source physical data provided for the model is not consistent with the figures of merit (FOMs) provided (meaning the actual FOM values resulting from physical parameters differ from provided FOM data), the model can tune the provided physical data to match the FOMs to the provided values. For more information, see Tuning Active Compact Models.

Field Type Description

IL

struct with fields described in table below

The overall insertion loss (dB) of the phase shifter at zero bias. 

 
Attn_eff

struct with fields described in table below

Attenuation efficiency (dB/mA) of the optical attenuator, as defined for voltage range described by "ref1" and "ref2" in the struct. 

 

Each struct above consists of following fields:

Note: The following variables can be provided as a 2x1 matrix if more than one mode is supported.

Field Type Description

tuning

boolean

A flag to enable or disable FOM tuning.
min

number

Minimum allowed value in SI unit if visible_to_user is set to True.
max

number

Maximum allowed value in SI unit if visible_to_user is set to True.
ref1 (if applicable)

number

 Point(s) at which the nominal FOM were measured. This parameter can be voltage or power data points depending on the FOM definition.
ref2 (if applicable)
 

number

 

Complete data requirement (for advanced users)

The advanced data section provides a complete reference of data supported by the variable optical attenuator model including the basic required data described in the previous section.

The description of all the fields in the source data template are described below.

general

"general" is a struct with following fields:

[[snippet||11549514081811]]

ports

"ports" is a struct with following fields:

[[snippet||12092461714963]]

Each struct above consists of following fields:

[[snippet||11549759363603]]

parameters

"parameters" is a struct with following fields:

[[snippet||12092500096659]]

Each struct above consists of following fields:

[[snippet||11720299494931]]

model_data

"model_data" is a struct with following fields:

[[snippet||12115391452563]]

bandwidth_data (optional)

struct

The 3-dB cutoff frequency (Hz) of the electrical modulator as a function of bias voltage (V). The required fields are:

  • bandwidth: 3-dB cutoff frequency (Hz) data points as a matrix.
  • voltage: Bias voltage (V) given by \(V_{bias} = V_{anode} - V_{cathode}\) data points as a matrix.

Note:

  • This parameter is optional and should only be provided to capture bandwidth effects.
  • Bias voltage is defined as, V_bias = V_anode - V_cathode.
  • At least two data points must be provided.
IV_data

struct

The current data, as a function of voltage and temperature, in the form of a struct with the following fields:

  • voltage: Vx1 matrix containing the voltage (V) data at which the current values have been provided.
  • current: Vx1 matrix containing the current (A) data corresponding to voltage points.

Note: At least two bias points must be provided.

waveguide_data

struct with fields described in waveguide_data table

Data required for modeling the waveguide sections.

waveguide_data 

Note: The fields are only required for waveguide sections with non-zero length. See Internal Model Diagram in photonic model page for a diagram showing the role of each section. 

Field Type Description

wavelength

number

Center wavelength (m) of the band for which the mode properties are provided.

temperature

 number

Temperature (K) for which the mode properties below are provided.
waveguide_passive_right

struct with fields described in table below

 

Mode properties for modeling the right and left passive waveguide sections
waveguide_passive_left
waveguide_transition_right

Mode properties for modeling the right and left passive to electrically active transition waveguide sections
waveguide_transition_left
waveguide_phase_shifter

Mode properties for modeling the electrical phase shifter waveguide section at 0 V bias

Structs listing mode properties for different waveguide sections consist of following fields:

[[snippet||11653970537235]]

FOMs

"FOMs" is a struct with fields below. This data is required for CML Compiler to run quality-assurance tests on the final model. It is also optionally used by CML Compiler to fine-tune the internal model to provide the expected behavior.

If the source physical data provided for the model is not consistent with the figures of merit (FOMs) provided (meaning the actual FOM values resulting from physical parameters differ from provided FOM data), the model can tune the provided physical data to match the FOMs to the provided values. For more information, see Tuning Active Compact Models.

[[snippet||12116770242323]]

Attn_eff

struct with fields described in table below

Attenuation efficiency (dB/mA) of the optical attenuator, as defined for voltage range described by "ref1" and "ref2" in the struct. 

Each struct above consists of following fields:

Note: The following variables can be provided as a 2x1 matrix if more than one mode is supported.

[[snippet||11653867902995]]

QA

"QA" is a struct with following fields:

[[snippet||12117860577811]]

statistical 

"statistical" is a struct with fields below. This struct is optional and is only required for statistical compact models.

Note: To allow CML Compiler to build statistically enabled models, the statistical_parameter_status has to be defined in the XML file. For more information, see Statistical CMLs.

Field Type Description
parameters

struct

Each field of this struct defines one statistical parameter for the model. These fields should have names following "parameter_X" where X is an integer and follow the structure described in statistical parameters table.

Note: This data is required for CML Compiler to enable statistical modeling.
QA

struct with fields described in QA table

Defining QA settings for statistical QA.

statistical parameters

[[snippet||11647965606547]]

slope_neff

number

 

 

 

The sensitivity of the effective index of the active waveguide with respect to the X-th statistical parameter defined as d_neff / d_parameter_X.

Note: Only provide this field if the statistical parameter affects the effective index (see voa_stat_te_c). 
slope_ng

The sensitivity of the group index of the active waveguide with respect to the X-th statistical parameter defined as d_ng/ d_parameter_X.

Note: Only provide this field if the statistical parameter affects the group index (see voa_stat_te_c). 
slope_Attn_eff

The sensitivity of the Attn_eff (dB/mA) of the optical attenuator with respect to the X-th statistical parameter defined as d_Vpi_Lpi/ d_parameter_X.

Note: Only provide this field if the statistical parameter affects the Attn_eff (see voa_stat_te_c).
slope_IL

The sensitivity of the insertion loss (dB) of the electrical phase shifter with respect to the X-th statistical parameter defined as d_IL / d_parameter_X.

Note: Only provide this field if the statistical parameter affects the insertion loss (see voa_stat_te_c).

statistical QA

[[snippet||12118523234707]]

Associated files

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